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About this blog

Moto Mind is a technical blog written by Paul Olesen who is a powertrain engineer working in the motorcycle industry. The blog covers a wide variety of topics relating to two and four stroke engine performance, design, and optimization.

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How Much Does It Cost To Rebuild A Four-Stroke Engine?

How Much Does it Cost to Rebuild Your Four-Stroke Engine? What costs are associated with rebuilding your engine? This is a topic that I see over and over again here on the forums and I have decided to take it head on. This question has many layers to it, and in order to answer it properly there are a few more questions that need to be asked. Are you going to let your wallet get roosted at the shop and trust that the mechanic does their job? Are you going to brave the tool box and try do it yourself? The bottom line is if you want to save money and be sure that your bike is well taken care of the answer involves a little bit of both. To start I wanted to get an accurate picture of what shops are charging across the country to do a full rebuild, top end servicing, and other various maintenance tasks. This includes what the OEM dealers are charging and recommending as well as the non-dealer private shops. Along with the OEM vs. Non-OEM differences I wanted to see if there were any differences between geographical regions. I guarantee you, this experiment was nothing short of interesting. The Plan: I would call eight shops in total across four different regions of the United States. In each region I would call one OEM shop and one non-OEM shop. To be a bit more specific, the regions I focused on were the Midwest, the South, the East coast, and the West coast. All the shops were found using Google Maps and then selected based on the quality of their website appearance. If I found on their website that they were qualified to do engine rebuilding and servicing, then I considered them a worthy candidate. Another grading system I used to select which shops to call was the Google rating they had when you searched for them online. This includes the number of reviews and a 5 star rating scale. Whichever shops in each region had the most reviews and the highest ratings I selected to experiment on. As consumers we are drawn to professional well-organized websites that have testimonials that instill trust, so all else being equal, I decided these were the best ways to select the shops for my experiment. The Scenario: Along with getting prices for services, I wanted to see what shops were recommending when it came to service intervals and part replacements. The best way to do this was to introduce myself as a fairly new rider who just bought an eight year old bike. In my eyes, new riders are the most vulnerable when it comes to being mislead or price gouged so they would be a perfect subject to use for the call. I also assumed that shops would be more willing to answer my “new rider” questions because it ensures that they help beginner riders get going in the sport, as well as want to come back to their shop come service time. I began each call by raising concerns about the integrity of the bottom end of the engine. I stated that the bike was a 2006 Honda CRF450 with around 200 hours on it. I asked if the bottom end should ever be replaced and what a full rebuild would cost. I also asked if there were any tests that could or should be performed to check the integrity of the bottom end. Once my bottom end questions were addressed, I proceeded to ask about the top end and how often the piston should be replaced. I asked about the price of top end services and what that service entailed. I also asked specifics about the inspection of cylinder head and if the valves ever need to be replaced. The Outcome: Naturally conversations shifted and answers took me by surprise, thus making simple side-by -side comparisons of all the shops’ answers impossible. So for your enjoyment (or dismay) the most fair and accurate way is go through each individual shops’ conversation with me ,summarize them, highlight their price, and recommendations. Prepare yourself for the good, the bad, and the ugly. Midwest OEM I introduced myself and explained to the service department that I had a 2006 Honda CRF450 that I was considering having fully rebuilt. I was a new rider, the bike was raced from time to time by the previous owner, and it had over 200 hours on it. I wanted to know what a full rebuild would cost and if they thought it was necessary. The service department asked me a few questions about the top end and if there was any damage to the bike, and asked if I wanted just the top end “freshened” up. I said no, there was no damage to it. I replied that since the engine had so many hours on it I was worried about how long the bottom end would last. He put me on hold for about 10 seconds, then picked up and told me that a full rebuild would be, “very, very expensive, many hundreds of dollars,” then asked for my name and number, and said he would get back to me on a price. It’s been over 10 days and this shop still hasn’t returned my call. What are my thoughts on this? Out of all the shops I phoned I felt like this one may have been the most fishy. No other shop I called willingly let me talk them into rebuilding my bottom end and they all told me it wasn’t necessary. My conversation with the service department was short and they really didn’t have much advice for me but were willing to do the work. “Many, hundreds of dollars?”, a full rebuild will most likely cost over 2000 dollars. I don’t think the right questions were asked on their end about the maintenance history of the bike, the price was misleading, and from what I gathered they didn’t have much experience working on this particular model. West OEM I introduced myself, my concerns with my ‘06 CRF450, told them about the 200 hours on it, and asked about a full rebuild or any advice they could offer concerning caring for the bike. The shop guy who answered said with 200 hours that the bike has to have had a few top end replacements done already. I questioned him on the need to do the crank bearings and he immediately said, “Not necessary, not necessary. I’ve got an 02’ myself and it has the original crank in it.” He then went on to assure me that all the problems come from, “...top-end stuff. Valves and pistons, not crankshafts.” But then he immediately contradicted himself and someone he knew blew a crank out, “But to predict it and just throw a crank in because of maintenance, that’s all up to you. That’s a couple thousand dollars worth of work.” Instead he suggested just doing a valve adjustment, “With a valve adjustment we could tell what size shims are needed to adjust the valves and from there tell how much wear and tear is on the top end.” I then asked if there really was no way to know when a crank will blow out and he said, “It’s more about maintenance, making sure the oil is clean, and things like that that take care of the bottom end. If you blow a clutch up and don’t clean out the bottom end properly those pieces can contaminate the bottom end and cause other problems. If you’ve been taking care of the bike and changing the oil then the bottom end should be fine.” He then told me that the piston needed to be replaced every 15 hours of riding per the factory service manual recommendations. He then offered to do the valves for me, but said we might as well get a new piston in while we are at it. I asked him how much this would cost and his reply was, “Depending on what’s going on you’ll spend 500, 600, or 700 bucks. I’d say I’d have 500 to 1000 ready to go depending on what’s wore out. You know 700, 800 bucks is usually pretty close.” I then asked him about the service interval for the valves, just to get a picture on how much this would cost me over time. He then stated that it was related to the maintenance of the air filter, “If the air filter isn’t maintained properly, it has a little rip in it, or gets a little dirt in it that is what wears those valves out. You can have bad air filter maintenance and wear those valves out in one ride because they are titanium and hard coated. Once that hard coating wears out then that valve wears out extremely fast. So if the engine ingests a little bit of dust or dirt then the valves can go away pretty quick. Stainless valves are a lot more durable. The valves that we put in it are out of the TRX450.” I thanked him for his input and said I would think about it. My thoughts? I thought that this shop was the best out of all the shops I spoke with. I think the service guy did the best he could to help me however I still think there were some contradictions and flaws with the advice he gave me. One of the troubling things that is a theme throughout my conversations is the bottom end question. All the shops were adamant that it’s not necessary to replace the crankshaft or bearings yet as highlighted in this conversation even the service guy knew someone who had a bottom end let loose. So as consumers the question has to be “should the bottom end ever get replaced or not?”. This in my opinion is dependent on the type of riding that is being done. Being told the piston must be replaced every 15 hours bothered me a little bit too. I understand that the factory service manual states this and I know that is the reason the service guy told me this however the service manual intervals are for bikes that are being raced. I wasn’t asked how I was riding the bike and think for anyone not racing replacing a piston every 15 hours is a bit excessive and expensive. The service man’s general info on maintenance and the repercussions of not maintaining the oil and air filter are spot on along with his input on valve maintenance. The shop rates while fluctuating I think are in the ballpark for what someone might expect to pay since the amount of work required on a top end can be minimal or significant depending on the condition of the engine. South OEM Service manager was out to lunch. A message was left but my call was never returned. My thoughts? As a business I would think it could be profitable to return a customer’s phone call? East OEM I introduced myself and my bike, as well as my concerns about servicing it after 200 hours, as usual I asked for a full rebuild, raised concerns about the bottom end, and if the crank needed to be replaced. The shop told me right off the bat that you never need to touch the bottom end on a four-stroke. It never needs to be serviced or replaced. I asked again, just to be sure, and brought up the fact that I knew that some two-strokes could come out of true, and he assured me, “Nope, nope, that’s the beauty of having a four-stroke.” So then I raised concerns about piston replacement and the valves, to which he replied, “Valves, yeah, not so much replacing them. Just making sure they are in spec. What year did you say? 06’? I said yes and he put me on hold for two minutes. When he picked up he informed me that on my make and model I need to come in at least every 10 hours of riding to have the cylinder head inspected and perhaps the valves adjusted. It would cost me around $160 each time, or $200 if the shims needed replacing. (This service involved disassembling the head and using a valve guide gauge to check the diameter of each valve guide) Cue my mind exploding. Then he went on to tell me that if I just bought it to get it done regardless, “Because you know, I think something in there is aluminum on the older models and they heat up and not hold up and then you get the cherry red exhaust pipe. That’ll end up messing up your head.” Okay… He also told me that, “the newer ones were made with magnesium, and like, tougher things, so, you know.” (Magnesium is softer than aluminum, has a lower melting point, and unless combined with another alloy would never be used for any part of a cylinder head by the way). I asked him about the piston, to which he replied, “Now that’s one of those things like the crank. Being that it is a four-stroke it is not taking a beating like the two-stroke bikes. You leave that alone. If it goes, then that’s something that happens but there’s no replacing those either. It’s mainly all valve jobs on that thing.” I thanked him for his wisdom and time. Where do I even begin on this call? Sometimes I think the folks answering the phones at the shops feel they must give you at least some advice, right or wrong, when it would be much preferred if they just conceded that they don’t actually know. In this case the man I spoke with chose the route of telling me lots of wrong things. This call was by far one of my worst conversations, and I was left wondering how the service men that were fielding my questions are in the roles they’re in. The advice on never changing the piston is wrong, the head does not need to be taken off every 10 hours to check the valve guide bores, and I’m certain magnesium is not the saving grace for the newer Honda cylinder heads. Midwest Non-OEM I introduced myself and my bike, I asked about the bottom end needing servicing, what it might cost to service the piston and the valves, and I told the guy I was trying to familiarize myself with maintenance schedules. The guy told me it all depends on parts availability and pricing. He said his shop charged $60 an hour. I asked him again about the crank or the valves, trying to get some more information on service intervals, etc. But he replied curtly that it would be about an hour and a half of servicing, so $90 in total. I thanked him and hung up. My thoughts? The theme I noticed with the non-OEM shops is that they were all much less familiar with my particular make and model. This I believe is due to the fact that they work on anything and everything and don’t see the same type of bike frequently enough to proficiently give sound advice. In the case of this shop my main questions were dodged and the best I could do was get a shop rate and a price for adjusting the valves. The person on the phone was not particularly helpful nor pleasant to speak with making it hard to want to continue my conversation or consider doing business there. West Non-OEM Per usual I introduce myself and my bike, tell them I’m a new rider, ask about the bottom end and other services. The shop guy told me that the best way to know would be to bring it in and have them look at it. He took a moment to speak to the service department and another guy got on the phone with me and told me, “You don’t have to check the bottom end at all. It’s usually all top end stuff. Unless your bottom end is going the only way I can check that out is by tearing your motor apart. And there’s no reason you should be tearing your motor apart.” He asked me again about the history of the bike and cut me off mid sentence and said that an oil change and valve servicing would be imperative. I asked again about piston replacement and he told me that it would cost $1000 to $1500 minimum. What? He told me, “Yeah, because I have to tear down the top end of your motor and rebuild it.” He then quizzed me about the type of riding I was doing, two points for them, and I told him I wanted to do a little bit of motocross practicing, but then he cut me off mid-sentence again and told me, “I think every 15 or 20 hours you’re supposed to have the valves inspected.” I started to ask a little bit more, but he curtly said, “Is there anything else cause I got customers standing in front of me.” Whoa, okay. I asked him one last time on the cost of the piston replacement and if that included the valves being checked to which he said, “Don’t hold me too that. That’s why I said it could be 1000-1500 dollars. It could be a little bit more.” I thanked him for his time and hung up. My thoughts? The service man on the phone was pretty rude, asked a few of what I consider the right questions, and then gave me an awfully high price to overhaul my top end. I wanted to know more about what his top end overhaul entailed but he clearly didn’t have time to help me so the conversation was cut short. As rude as the man was I would think it would be difficult to attract business if he acted that way all the time. South Non-OEM After introducing myself and my bike, asking about the bottom end, the piston, etc. They guy told me to just take it to a Honda dealership. He said there was no way of checking the bottom end without tearing the engine down. He told me with approximately 200 hours on the thing, “I wouldn’t be that concerned about it.” He prompted me again to call a Honda dealership to get more maintenance interval information, but that his shop could perform any of the work needed. Right. I asked him again about the cost of replacing the piston. He stalled and said that he would have to get back to me on that one. He took down my number and told me he would call me back. It’s been over 10 days and the shop hasn’t returned my call. My thoughts? I appreciate this shop’s honestly. The person I spoke with wasn’t that familiar with my bike and didn’t hesitate to try and point me in the right direction by directing me to a dealer. The advice he gave was indicative that he didn’t know a whole lot about the bike. While it’s possible he was fully capable of performing any work I would prefer the person doing the work know a bit more about the bike. East Non-OEM I introduce myself, my bike, ask my gamut of questions. The shop guy tells me, repeatedly, you can’t check the bottom end without removing the top end. So I ask about the top end and tell the shop guy, “Well the previous owner said he did it every 40 hours and there are about 20 hours on it since he last did it. Was his service interval right or should it have been done more or less?” He asked about the type of riding the last owner was doing, two points for this guy, and I told him a little bit of racing, to which he replied that those intervals were normal. So I asked how much it would cost to overhaul the top end and he told me, “Well the cylinder head has to be sent out so you’re probably looking at around 750 bucks.” He asked me how I was planning on riding the bike and I informed him just around on the trails, nothing too hard, and his advice was, “Yeah, I would ride it. When it starts losing power and becomes hard to start that means the valves are going to need to be looked at and at that time we can check out the top end.” I thanked him for his advice and hung up. My thoughts? I’m going to assume the service man was talking about checking rod end play, small end diameter, and axial free play when he said the top end would have to come apart to check the crank. With the crank still in the engine the run out wouldn’t be able to be accurately checked. As I wrote in one of my previous posts about service intervals offering specific advice on when to service a particular part is difficult. It was refreshing not to hear every 15 hours or never replace the piston. Whether every 40 hours is right or not would require further information on the experience level of the past racer. The cost to service the top end sounded like a competitive price especially if any head work was going to be done. The service man’s advice on when the bike might need attention was also in alignment with what I have previously written. As you can see the information provided by the various shops was sporadic, lukewarm, and in some cases - plain wrong. This is a complete shock to me, I have to be honest and say that I expected a bit more out of these shops, OEM and non-OEM alike. I assumed that the training of those running and working in these establishments was to a high enough level that the only thing that would vary would be the cost of a particular service. I never imagined the advice and service intervals would be so terribly misleading. This whole experiment became a can of worms, but I am glad I took it upon myself to do it because it shows me that educating myself and working on my own bike all these years was the better choice. Based on the answers the shops gave me, it is imperative that consumers do some serious research before selecting a shop to perform internal engine work. You need to be asking the right questions and the shop needs to instill the confidence that they are capable of doing the work, before you hand over $2000+ for a full rebuild, or $750 to $1500 for a top end overhaul. The lesson here is if you want a shop to do the work, take the time to be absolutely sure you are getting your money’s worth and that they are a knowledgeable source. Based on my experiences dealing with the shops I think a consumer can greatly increase their chances of finding a great shop by searching for shops that specialize in a particular make, model, or segment of the market. For example I would expect the competency of dirt bike specific shops to be much higher than the all make and model variety. Here’s the thing about running a shop though- the prices they charge are justifiable because that high price is what keeps their business going. I understand that and I wouldn’t mind paying them if the majority of theses shops could provide a concrete answer to my questions. The problem for some folks is that power sports are expensive enough, without bringing in a mechanic to help repair their engine. If a consumer can't afford to have a professional fix their bike they either have to do it themselves or they end up leaving the sport. With land closures, environmental regulations, and the high costs associated with dirt biking - the sport is already in decline. We cannot afford to lose riders because they don't know how fix their own bike or can't afford to bring it to a shop. I see this as a serious issue because the life of this sport is dependent on a bike that runs and a rider that is excited to get out and tear it up. So how do we keep the money in our pockets and make sure our bikes are cared for properly? After seeing for yourselves the varying degree of information given by shops some of you might be wondering why I haven't disclosed the names and locations of the shops I called. In some cases I would like to, but the point of this article is to outline the costs, varying degrees of knowledge, and competency of the shops. I want this write up to be an educational insight into the industry and don't intend to harm individuals or businesses. As consumers you are the ones that need to decide for yourselves who does your work by asking the right questions and educating yourselves about your machines. There is something indescribably cool about knowing how your bike and engine go together. Whether it’s saving yourself a chunk of change, knowing how to care properly for your bike, or just learning something new and mastering it. So how much does a full rebuild cost you when you do it in your own garage? When you are using OEM parts, which includes all new bearings throughout the engine, a cylinder head, new valvetrain, new crank, new piston, new cam chain and tensioner, and a freshly honed cylinder, the cost comes to $1300 to $1500. I have a complete parts list you can check out by clicking HERE. So compare that price to $2000+ and suddenly doing the work yourself doesn’t seem like such a bad idea, also add in the coolness factor of learning how your bike goes together and knowing you rebuilt an entire engine on your own. Another thing to consider is that you will have this knowledge forever and it will extend the life of your bike(s) and your bank account for many years to come. And how about the cost of a top end overhaul in your own garage? This could run you as little as $260 for a piston replacement, which includes a new piston, rings, circlips, head and base gaskets, and a freshly honed cylinder. Pretty inexpensive right? On the flip side a severely worn out top end which needs every bell and whistle replaced, aka the cylinder, the head, and valvetrain components could cost you $900 in OEM parts as well as machine work being done on the head and cylinder. Again, compare this to the $750 to $1500+ range for an in-shop piston replacement. The top end parts list can be viewed HERE. These at-home mechanic perks are dependent on you putting the bike together correctly though, because if you don’t it can cost you big time. When I first started tearing into my own bike I made a lot of mistakes that I wish I could have avoided because it did end up costing me in the long run. Looking back now on those rookie rebuilds, after my education as a powertrain engineer and having designed and built an entire race bike, there were so many things I could have avoided. The only thing available to me back then was a factory service manual, but without good pictures and a well written step-by-step process it was a complete headache. For someone who is just getting into the whole rebuild world, those manuals are like trying to read another language. All I kept on wishing is that I had a mentor to learn these things from properly. Trying to watch free how-to videos online is a complete mess as well. After watching as many of these free videos online that I could find, as a professional I wish I could shout from the mountain tops to beware. These videos are poorly made, the information is spotty at best, and the mistakes that can be accrued from trying to reference them can be costly. So how and where do you even begin to learn how to rebuild correctly? When I truly began to learn how to fix things the right way, was when I started pursuing an education and career in the motorcycle industry. By working with highly skilled and experienced engine builders and engineers on a vast array of different engines, I learned that attention to detail is such an important aspect of rebuilding a healthy engine. Another key to success was having the right tools (look forward to a future blog post on this) and taking the time to measure things precisely (again, a future blog post). As I began to rebuild engines more and more, I realized that there are steps in which you need to trust a professional to do the work. For any at-home mechanic guy or gal, you can honestly do 90% of the work yourself and save a huge chunk of change. That other 10% can be farmed out to a competent machinist or shop at a miniscule fraction of the price versus trusting a shop to do the whole thing. So how do we bridge that gap for the riders who want to learn how to rebuild their own engines the right way and save themselves money? My aim is to empower riders from garage to trail. That means teaching you how to professionally tear open your own dirt bike so that you save money and know the work is done right. DIY Moto Fix is a business that wants to work with riders that want to learn how to work on their own engines, learn something new, and become an at-home mechanic master. Maybe you don't want to pay the high costs associated with a professional shop or you don't trust the work performed by professional shops. Perhaps you're just starting out and don't have a mentor that can teach you the ins and outs of rebuilding your own engines. I feel as if there are a lot of riders out there that would love to do the work themselves, if they could only find a credible source to learn from, and that’s where DIY Moto Fix comes in. Learning the Professional Way: We put together high quality HD how-to videos that teach you how to professionally rebuild your own engine. These videos are instantly downloadable, you can watch them on your mobile phone or home computer, and they come with a wealth of information that teaches you about your engine step-by-step. The beauty of these videos is that they include absolutely everything you will need to do a full rebuild - all the necessary torque specs, tool call-outs, new part numbers, and sequences. It completely eliminates the need for a service manual, any online searching for tips or tricks, or the endless quest to reference dealer part numbers. In addition, we teach the how and why behind each step so you come away with a better understanding of how the engine goes together. These videos are a credible source of information created for the everyday rider. Think of them as an Engine Rebuild Master Class. I am so excited to bring this level of knowledge and skill to the people who could benefit from it the most. This is the way we keep this amazing sport alive, by empowering and educating ourselves and saving money. If DIY Moto Fix could create an army of knowledgeable at-home wrenchers - we could die happy. Conclusion on Rebuilding Your Own Engine: When you think of the amount of money you can save over time by learning how to rebuild your own engine, when shops charge between $60 and $100 an hour, we’re talking thousands upon thousands of dollars. Another way to look at it is the amount you would save on one full rebuild at a shop is equal to the amount you could invest on the proper tools to do it yourself, over and over again. I would love to invite you to become a professional grade at-home mechanic and learn the correct way with DIY Moto Fix, whether you are a rebuild rookie or someone who is working to become a DIY master. If you are a CRF450 owner, someone who is interested in learning more about full engine rebuilds, or our master rebuild class - sign up by clicking the button below and we will send you all the information you need to get started. Send me the FREE Four Stroke Engine Rebuild Tools Guide For those of you that enjoy reading about engine rebuilding, I published a comprehensive book which details the fine intricacies often overlooked by amateur engine builders. The book covers a variety of topics including diagnoses, how engine parts are manufactured, precision measurement tools, disassembly, inspection, and correct assembly techniques. Do you have a shop horror story you want to share? Did you recently have your engine rebuilt and want to share how much it costs? Do you like the idea of educational how-to videos that teach you how to rebuild your engine? What other things could we produce for you that would help you as an at-home wrench and rider? As always, I enjoy hearing your thoughts and comments. Moto Mind- Empowering and Educating Riders from garage to trail DIYMotoFix.com

Paul Olesen

Paul Olesen

 

Who Warms Up Their Engine Anyway?

Whenever I’m out and about either riding my motorcycle or participating in racing events occasionally I see things that just make me wonder “why”? One of those moments is when I see someone take a cold bike and fire it up for the first time and bang it off the rev limiter, start riding it immediately, or annoyingly continuously blip the throttle as if it will never idle on its own. These actions beg the question, “Why is it important to warm up an engine”? The answer lies in a simple explanation of science and mathematics. Before you quit reading because you may not have been an ace at math and science in high school, just give me a minute to break it down. It is actually really simple. The whole reason we need to let our engine warm up revolves around the concept of linear thermal expansion. Your engine is made up of a number of different materials. The piston is made from a certain type of aluminum alloy, the cylinder another type of aluminum alloy, the rings cast iron or steel, the valves if you have a four-stroke from steel, stainless, steel, or titanium, and the guides are made from yet another material. Once the engine is started these components begin to heat up from combustion and friction as they slide back and forth. None of these materials are exactly alike, and because of this they will expand when heated or contract when cooled at different rates. This interaction between material and change in temperature is predictable and linear. Now that we understand that engine components change dimensionally from when the motor is cold to when the motor is warm we can start to see the importance of warming up the engine. When a cold engine is first started the piston heats up and expands first. Heat is transferred from the piston to the rings and then to the cylinder wall. If we rev the engine and generate lots of combustion cycles and increase the frequency of friction too early the piston will grow much faster than the cylinder. If there is not adequate space between piston and cylinder to account for this growth the engine could suffer what is known as a cold seizure and you will have yourself a bad day. By allowing your engine to warm up before you start riding you allow all the components in the engine to slowly expand and stabilize. Once the engine is warm, changes in the engine part dimensions are less drastic and there is much less risk of damaging the engine. The picture below shows an engine which was limped home after the coolant started leaking out. As the engine lost its ability to cool down, things began to tighten up. You can see how the piston contacted the cylinder evenly around the bore and created the vertical scuff marks. Even though this engine didn’t completely seize, you can imagine the severity of scuffing would be much worse for an engine that would seize. So you are probably wondering, “how do I know when my engine has properly warmed up then?” and, “what exactly do I do to properly warm it up?” The procedure for warming up the engine is simple. 1. Start the engine using the choke if necessary 2. Once the idle comes up due to the choke turn the choke off 3. Allow the engine to idle with the choke off until the cooling system warms up and the engine comes up to temperature. Knowing when the engine is ready to ride is a bit subjective. As you begin to pay closer attention to your engine, you will begin to detect when it is ready to ride. Personally for water cooled engines I like to feel the radiator and use that as an indicator. I place my fingers on the side of the radiator where the coolant is returning from the cylinder head and lightly touch to get an idea of how warm the coolant is. I do this until the radiator is just getting uncomfortable to touch. This typically only takes a few minutes and after that I’m ready to start riding the bike. For air cooled engines my approach is much the same except I feel the cylinder and head to determine when I think the motor is warm enough to ride without causing any unnecessary wear or damage. Paul If you'd like to follow my blog, click the "follow this blog" button in the upper right. I'd love to have you.

Paul Olesen

Paul Olesen

Are Project Bikes Even Worth It?

Whenever purchasing a used dirt bike, no matter how well inspected, there is always an element of chance involved. The possibility of an engine failure is what worries everyone the most and is a costly disaster to deal with. For those mechanically inclined, seeking a blown up bike can be alluring because it allows the new owner a fresh start. While this may seem like an ideal situation how often does it financially make sense and how do you decide to make the purchase? At DIY Moto Fix we just picked up a 2006 Honda CRF250R “Project” over the weekend, and I want to share the financial reasoning that went into the purchase as well as discuss the critical inspections we made which led me to pull the trigger. Over the next several months we’ll see if I made a good decision! The criteria I intend on using to determine if my purchase was justified or not will depend on a couple things. First, if I sell the bike will I net more money than I have into it, or at the least, break even? Second, could I have spent an equivalent amount of money elsewhere and gotten a bike that has a freshly rebuilt engine, which to me, equates to a machine that will provide countless hours of trouble-free riding? The bike will also be the subject of several blog posts and perhaps videos. However, these uses will not be factored into the valuation of the decision. No corners will be cut throughout the rebuild, and the end result will be a robust bike that I would be proud to keep, should I choose to. That said, let’s take a look at what I picked up! The Bike I found the bike listed on Craigslist for $1000. There wasn’t much detail behind the ad, and it consisted of a couple of sentences. In summary, the ad basically said everything was there, a new crankshaft and main bearings were included as well as a new top end. A half dozen pictures were presented and the engine was neatly laid out. I contacted the seller and inquired if any engine components were missing or needed replacement. I was reassured the only things missing were the valve keepers! While it would be great to think the engine could easily be reassembled, I had my doubts. I needed to investigate in person. Preparation If you’re ever in a situation where you need to collect an engine in pieces, don’t rush and forget to come prepared. Some engine components shouldn’t get mixed around or interchanged and it’s incredibly helpful to keep the hardware separated by subsystems. Here’s a list of the storage aids I brought with: Sharpie marker Ziplock bags Boxes Plastic part bins The Real Story When I arrived, I was greeted by an avid rider who was friendly and had four seemingly well-kept bikes in his garage plus a bunch of moto-related parts, not a bad start. He showed me the 250R he was selling and I began my inspections. Inspections In most cases the engine internals aren’t accessible when looking at used bikes for sale, so as funny as it may sound, it can be really easy to get caught up in the excitement of the potential sale and forget to look at a lot of critical parts. Each major engine component that gets overlooked can be a several hundred dollar mistake and make or break the profitability of the purchase. I want to cover the engine internals I carefully inspect to estimate the cost of the rebuild. VIN Number I’m a practical person and highly recommend ensuring the VIN number is unmolested and the seller’s “sale story” remains consistent throughout the sale. Don’t bother inspecting anything else if the VIN number has been tampered with. On some bikes, such as this one, cable chafing wore through part of the VIN number. This type of wear is easily discernible from intentional tampering. Crankcases Crankcases are one of the most expensive parts on an engine to replace, so look carefully for cracks and other damage. Scrutinize bearing bores, seal bores, threaded holes, cam chain guide slots, gearbox features, and mating surfaces. In this particular case, both the left and right case halves were damaged. I’ve got a lot of work ahead of me to try and bring these back. We’ll discuss welding crankcases in an upcoming post! Crankshaft Check the crankshaft to ensure it is at the very least serviceable. Look for surface damage, worn or broken gear teeth, and pitting. I recommend always assuming the crankshaft will require a rebuild even if it feels okay. Fortunately for me, this bike came with a new Wiseco crank assembly. Bearings All the engine bearings should be checked for notchiness. Any bearings that are gritty or bind when rotated should be replaced. For this particular engine, I’m planning on replacing them all. Conrod I recommend installing a new rod in conjunction with servicing the crankshaft. However, if you’re considering using the crank assembly, inspect the rod small end and feel how the big end rotates. Look for pitting and signs of distress in the small end. Notchiness in the big end warrants further investigation. Cylinder Inspect the cylinder walls for damage. Any defects you can catch your fingernail in should be cause for concern. The cylinder that came with this engine will either be replated or replaced. Piston/Rings The condition of the piston and rings can help determine what may have led the engine to be sold in pieces, however, reusing it isn’t something I’d recommend. Get in the habit of automatically budgeting for a new piston assembly anytime you come across a project bike. Cylinder Head The cylinder head is an expensive assembly to replace. While you always want it to be okay, I’ve found that by the time the bike reaches “project” status many of the internals, including the cylinder head, are in need of major TLC. Occasionally the valve seats can provide insight, however, I prefer to look at the valves themselves. Inspect the combustion chamber, head gasket sealing surface, and threaded holes in the cylinder head. Stripped fastener holes in the cylinder head can be very challenging to fix. On this engine, the valve seats will need to be recut or replaced, at a minimum. Valves Take a look at the valve faces for signs of recession and damage. Severely worn valves will be visible to the naked eye. This is the case with my new acquisition. Camshaft Inspect the cam lobes and any associated bearings for damage. Any pitting present on the cam lobes will warrant replacement. I’ll be installing a new cam in this engine. Transmission The gearbox shafts and gears should be inspected carefully for damage. On machines that don’t shift well and pop out of gear, damage to at least two mating gears will preside. Look at the gear dogs for excessive rounding as well as the mating slot. On this 250R the gearbox is in great shape. Clutch The clutch is an easy component to inspect visually. Look for basket and hub grooving which signifies a worn out clutch. In my case, this was easy to spot. Bike Inspections I’m not going to deep dive into the bike inspections since we’ve discussed this in a previous post and put together a comprehensive guide on the subject, which you can find here. In this particular situation, based on the amount of distress the radiators displayed I have to assume they will need to be replaced. The rest of the bike was in okay shape and luckily for me, the seller had some spare plastics, spare seat, and new tank plastics, which helped sweeten the pot. Rebuild Estimate Replacement parts for different makes and models vary, but I tend to make rough estimates based on the table shown below. The table is presented in a la carte style so cost estimates can be determined depending on what components must be replaced. The next table details the components I’m expecting to replace on the Honda. In this particular case, I’m estimating I’ll have $1630 into the resurrection of the bike and engine. I bought the bike for $800, so I’ll have a total of $2430 into the machine if my estimate is correct. Keep in mind this excludes monetary consideration for my labor. Since I’m going to use the bike for multiple projects, accurately tracking my labor will be challenging. If you’re looking to turn a profit fixing project bikes though, it’s essential to have a handle on the labor associated with each project. Resale Value I did a quick search on Craigslist to see what 2004-2007 Honda CRF250R’s were going for. I found a smattering of list prices and reasoned that I could sell this bike for at least $2000. Now, going by the numbers that put me out $430, again excluding labor. Was it worth it?   As you can see from a financial standpoint this project probably wasn’t worth taking on, or was it? Apart from picking up a broken low-value machine and then completely rebuilding it, is there any other way to pick up a used bike that undergoes transformation and starts its life in your hands with a completely rebuilt engine? I highly value understanding the condition of my machines before I entrust them to carry me at high speeds past trees or over jumps so assessing the heart of the machine whenever practical is valuable to me. I also get incredible satisfaction from working in my shop and resurrecting a machine that may have otherwise been slated for the parts section of eBay. What about you? What is your take on project bikes? If you’re looking to expand your arsenal of skills when it comes to wrenching so you can take on more challenging projects, take a look at our two and four-stroke dirt bike engine building handbooks! The dirt bike engine building handbooks are nearly 300 pages apiece and share a wealth of knowledge you won’t find in your service manual when it comes time to rebuild your engine. Check them out on our website or on Amazon .   Thanks for reading and have a great week! -Paul 

Paul Olesen

Paul Olesen

 

How Much Damage Can An Improperly Cared For Air Filter Cause?

I thought this week it would be a good idea to share with you an example of what can happen when dirt gets passed an engine's air filter. This will be a short post, but a picture is worth a thousand words. In my next post I’ll go into detail on how to properly care for your air filter to help ensure that this never happens to you.   The series of photos below shows a sad case where dirt has found its way into the engine and wreaked havoc. The photos are all from the KX250F I bought on the cheap with the sole intention of rebuilding the engine and documenting the process for my book, The Four Stroke Dirt Bike Engine Building Handbook. Honestly, I couldn’t have bought a better bike for the project, nearly everything on the bike was worn out or screwed up from the previous owner.   Here is how the air filter and airbox looked prior to disassembly.
  Here is the back side of the air filter. The filter was completely dry. There was no grease on the sealing face of the filter or the airbox flange. In this particular case, dirt could have got into the engine through the filter or between the filter and sealing flange. The amount of dried mud in the airbox and on the bike also makes me suspicious that muddy water got into the engine instead of just dirt. I honestly can’t say for certain.     The airbox itself was also extremely dirty.     Once the engine was disassembled I carefully examined the piston assembly and cylinder bore. At first, I could not get any of the rings to move freely. Only after I had pounded a pick between the ring ends of the compression ring was I able to get the compression ring off. As I removed the compression ring, a load of sand came with it.   This photo of the compression ring doesn’t do the situation justice. Some of the dirt was actually removed from the ring as I handled it.
  Here is a close up of the compression ring. Note all the grit!  
  The oil rings didn’t fair any better, were just as stuck, and had a lot of dirt on them.  
  Here you can see dirt inside the ring grooves and at the edges.  
  Here is dirt I rubbed off the oil rings.     Miraculously (and fortunately for me) whether the engine sucked in dirty air or water, it happened quickly and stuck the rings to the piston so they could no longer seal correctly, and the engine subsequently lost compression and power in a hurry. This speculation is based on the fact that the cylinder bore showed no signs of excessive wear or damage and it measured well within the service limits. This is an outcome I never though possible and is hard to believe.   I hope you enjoyed this brief write up on the damage that can result from ingesting dirt, whether from abnormal circumstances such as dropping a running engine into a mud hole or simply neglecting to take care of the air filter when running the engine in dusty conditions. In my next post I’ll show you how to care for and install your filters so these problems don’t happen to you! Questions or comments are always welcome and I enjoy hearing from you all!   -Paul
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Paul Olesen

Paul Olesen

 

Filling Up At The Pump

How Residual Pump Fuel Affects Your Fill Up
This week I have a quick tip I want to share with you regarding buying fuel and filling up gas cans for your bikes. I know many of you, myself included, rely on premium grade gasoline dispensed from local gas station pumps to put endless grins on your faces. One of the downfalls of gas station pumps is that fuel from the previous sale is left in the hose. According to the American Petroleum Institute, the amount of fuel left in a gas pump's hose is around 1/3 of a gallon.   Generally speaking, when two fuels are blended the octane rating of the resulting fuel is approximately the average of the two fuels. So if you had a gallon of 87 octane and a gallon of 93 the resulting blend would have an octane rating of 90. I'll be the first to admit that 1/3 of a gallon of fuel added to a two gallon gas can won't have much effect on the octane rating. For those of you that like numbers, 0.33 of a gallon of 87 added to 1.67 gallons of 93 will yield the following octane rating:   0.33 gallon of 87 / 2 gallons = 16.5% of the total mixture
1.67 gallons of 93 /2 gallons = 83.5% of the total mixture   (0.165 x 87) + (0.835 x 93) = 92 octane blended fuel   So in a two gallon can, the octane rating of the fuel has dropped a point due to the 1/3 gallon of 87 in the pump hose. Unless you have a very well developed performance engine, this isn't anything to lose sleep over. I think a bigger reasons to want to keep that 1/3 of a gallon out of your can is due to the possibility of ethanol being in the hose from the previous sale. Many articles can be found outlining why ethanol should be avoided, but the main reasons include part corrosion due to the exposure to alcohol, rubber seals and o-rings may not be compatible with ethanol resulting in swelling and failure, and some plastics deteriorate when exposed to ethanol. Not to mention ethanol contains less energy than gasoline. Again, we're not talking about a large percentage of ethanol in the overall scheme of things but I prefer to stay away from the stuff when I can.   Fueling Tip
I'm very careful about what I run through my powersport engines. To safeguard against filling up a fuel can with residual fuel from the previous sale, I like to donate the first gallon of "premium" to my vehicle before filling my gas cans. This ensures whatever fuel was in the hose and pump is flushed out and that I'm filling up my cans with premium. If you are borderline OCD about what goes in your engines like I am, you may consider adopting this practice.   I suspect many of you have other tips and tricks regarding fueling. Leave a comment below and share your thoughts and experiences so other motorheads can benefit!   Book News
I also wanted to invite you to check out my book on how to build four-stroke engines, which is now officially available in print form. It took a ton of work to bring the print book together and get the right help on board. The project hasn't been easy, but I'm proud to offer this book to you and can assure you it will make a great addition to your workshop. You can learn more about the book by following this link: The Four Stroke Handbook   To celebrate the arrival of the print book, I'm running a sale until the 27th of September offering all versions of the book at a 20% discount. After the 27th the sale will end and the price will go up. If you've got a build coming up now or in the future and are interested in the book, now is a great time to pick up a copy.   Thanks for reading and have a great week!
-Paul  

Paul Olesen

Paul Olesen

 

Getting Started Servicing Shocks

Hey everyone, this week we're going to switch it up and talk shock absorbers! Over the last few months I've gotten many requests to broaden the topic spectrum and cover other dirt bike topics. So today, we'll do just that by discussing and providing some resources to get you familiar with servicing shocks.   I suspect many of you currently take your shock to someone to have it serviced when it needs to be freshened up. I also bet that it is usually a pain to be without a bike for perhaps a week and that it probably costs around $100 each time? I know I always dreaded having suspension work done on my bike because it seemed to take forever, plus I always had to drive over an hour and half to the nearest shop. For me, those days are long gone. Now do all my suspension work myself.   I believe the majority of you are completely capable of servicing your shocks yourself, but just don't quite have all the pieces of the puzzle you need. Maybe you're not quite sure what tools you need; or once you get the shock apart, you don't know what parts you will have to replace? To help clarify what's needed to service a shock and answer some of the common questions about shock building, I created a detailed guide for you. The guide will help you decide if outsourcing your shock maintenance is the way to go or if you are in fact ready to take the job on yourself.   Before I discuss the details of the guide, I want to provide you with a little background on shock absorbers. For major motorcycle brands, shocks are sourced from the following companies: Showa, KYB, and Works Performance (WP). These three brands are primarily the companies responsible for equipping OEM bikes. Companies, such as Ohlins, cater more towards the aftermarket. Out of the three common OEM shock brand options, Showa and KYB are the go-to's for the Japanese manufacturers, while European brands, such as KTM, gravitate toward the WP brand. So if there is any question as to what brand of shock you have, you can keep this in mind. Out of the three common OEM brands, Showa and KYB shocks are very similar, while WPs feature a slightly different design.   The guide I created is geared towards those of you with either Showa or KYB shocks. Those of you with WP shocks may still find the guide useful, but there are a couple tools missing. Within the eight page guide, you'll be provided information on all the tools you need to service a Showa or KYB shock. These tools include any specialty tools and discuss shock pressurization options. Plus there are some pointers on how to make your own specialty tools if you are on a budget.   Once you get through the tools section you'll be presented with a detailed outline on replacement parts. Knowing what to replace within the shock when it is due for servicing is extremely important and the replacement parts section will walk you right through what you may need. It will also provide you with different options for buying replacement parts.   To receive the eight page guide and learn more about shock servicing, click the following link: Shock Building Tools and Replacement Parts Guide     Thanks for reading and feel free to comment below with any questions or concerns. Bringing high quality DIY advice is what Moto Mind is all about, and I enjoy hearing from all of you and your DIY experiences.   -Paul Olesen
DIY Moto Fix

Paul Olesen

Paul Olesen

 

How To True A Dirt Bike Wheel Yourself

In my last blog post I covered how to lace up a wheel assembly with new spokes. This week I’ll discuss how to properly true the rim. Truing the rim is actually not too difficult. Once you understand the interaction between the spokes and rim, you will make quick work of the job.   To get started a truing stand of sorts needs to be set up. This doesn’t have to be anything special and I used a bench vice, adjuster block, rear axle, spacers, a series of old bearings and washers, and the axle nut. The reason I went to the trouble of clamping the hub in place was to eliminate any possibility of the hub sliding back and forth on the rim, which would make my truing efforts difficult.     This is by no means the only way to create temporary truing stand and you can use your imagination to come up with alternatives. Temporarily installing the wheel back into the swingarm may work equally well if you don’t have a bench vice.   Next, some sort of gauge will be needed so the amount of runout can be seen. I used a dial indicator attached to a magnetic base, however more simple solutions could easily be fabricated.     It isn’t absolutely necessary to measure runout, especially right away when major adjustments may need to be made. Instead you only need to see how the gap between the end of the pointer and rim changes as the wheel rotates. A coat hanger, piece of welding rod, or even a pencil could all be used to the same effect as the indicator shown.   Axial (side to side) runout will be corrected first. Here you can see there is a noticeable difference in gap size between the rim and pointer through a full revolution of the rim.     The goal is to tweak the tension in the spokes so that the gap between the rim and pointer is even as the rim is rotated.     To do this the gap can either be increased or decreased depending on which spokes are tightened or loosened. To decrease the gap, tighten the spokes originating on the side of the rim where you want the gap to decrease. In the previous photo I’m tightening the right side spokes, and in doing so I am pulling the rim to the right. An ⅛ to ¼ turn of the nipple is enough to induce a change. For the given area of the rim that must be pulled over, evenly tighten at least three of the surrounding spokes on the side being pulled. If the rim needs to shift a lot, loosen the opposite side spokes the same amount you have tightened the pull side spokes. This will help keep even tension on all spokes and help to shift the rim.   The process of tightening and loosening the spokes to pull the rim from side to side can be performed at all the high and low points surrounding the rim. Continue to turn and rotate the rim around until the gap between the rim and pointer evens out. Some areas may require tightening the spokes and pulling the rim one way while other areas may need to be loosened to allow the rim to move back the opposite way. Take your time and make small changes as you go. As I mentioned before, it doesn’t take much to see a significant change in rim location as the spokes are tensioned.   As the rim is fine tuned for side to side runout, the pointer can be moved closer to reduce the gap. Reducing the gap as the rim is trued will make it easier to see smaller differences in runout. To really fine tune things I like to use a dial indicator, setting the contact point up on the outer edge of the rim. Again, this isn’t absolutely necessary and similar accuracy could be achieved with a simple pointer.     Here I’ve snapped photos of the high and low points on the rim. The total runout is the difference between the high and low points. In the left picture the needle is 0.0075” (0.19mm) to the left of my zeroed point. In the righthand picture the needle is 0.008” (0.20mm) to the right of the zero. This gives me a total runout of 0.0155” (0.39mm). Most service manuals suggest a max runout of 0.079” (2mm) so I’m well within spec! Quite frankly I was very pleased to get the rim to 0.0155” since the rim is old and slightly dinged up.
The rim I was working on is centered on the hub. Some rims will be offset and it will be more important to pay attention to the relationship between the edge of the rim and a feature on the hub (usually the brake disc machined surface or the machined surface for the sprocket). Your service manual will provide specs for measurement points and specify how much offset should be present. Setting the offset correctly is important because if the offset is off, the front or rear wheel will not be inline with the other wheel. This can make the bike's handling very interesting! I don’t think a little misalignment is too noticeable on dirt, but it is definitely a problem on asphalt.   A straightedge can be used to measure from the indicated surface, outer edge of the sprocket, or brake disc to the edge of the rim. If measuring off the sprocket or brake disc, you’ll need to subtract the thickness of the sprocket or disc from your measurement.     If the rim is not quite positioned right after all the side to side runout has been corrected, it can be shifted at this time. To pull the rim one way or the other, simply evenly tighten all the spokes on the side you are trying to pull the rim to. The opposite side spokes can also be loosened to help allow the rim to shift over. Once the rim is set where it needs to be, half the battle is over!   Next, the radial runout must be corrected. To do this move the pointer so that it sits past the outer edge of the rim.     The gap between the pointer and outer edge of the rim will be monitored and tweaked to achieve evenness throughout the rotation of the rim.
This time to induce change in runout, all the surrounding spokes in the area will either be tightened or loosened evenly in unison. To increase the gap, as I’m doing in the following photo, all the spokes are tightened which pulls the rim inward, enlarging the gap between the pointer and edge of the rim.     To decrease the gap in a specific area all the spokes in that area can be loosened allowing the rim to expand outward towards the pointer. Just like with side to side runout corrections, the nipples only need to be turned an ⅛ to a ¼ turn to make noticeable changes in the gap.   As long as all spokes in the affected area are tightened or loosened evenly, the side to side runout will not be affected. Slowly rotate the rim and make the necessary tweaks until the gap between the edge of the rim and pointer is close to the same as the rim rotates around. The pointer can be moved closer and closer to refine the roundness of the rim. The surface of my rim was too beat up to take accurate measurements so I simply relied on eyeballing the gap to set its roundness.   Once the rim has been trued both axially and radially, the spokes will still be relatively loose. The spokes will all need to be tightened gradually and evenly so that all the efforts of truing the rim are not wasted. Since the majority of rims are either 32 or 36 spoke rims every 4th spoke around the rim can be tightened. This results in an even 8 or 9 step pattern which is repeated four times to tighten all the spokes. First all the red spokes are tightened, then the greens, yellows, and finally blues. Tighten each spoke ¼ turn at a time.   Alternatively, forum member ballisticexchris, suggested a pattern where every third spoke is tightened. This would allow the tensioning of both sides of the rim within the same revolution of the wheel. I've always had good results with the pattern I've outlined but believe his suggested pattern will work equally well and is another option for you to use.     As the spokes are tightened, not surprisingly, the nipples will become harder and harder to turn. The evenness of the spoke tension can be checked by tapping the end of the wrench against the center of the spoke. The spokes will emit a ringing sound and the pitch will be different for spokes which aren’t the same tightness. Continue to work your way around the rim gradually tightening the nipples until all the spokes are similarly tensioned.   Next, use your hand to squeeze the spokes which are parallel to each other together. Squeeze all the spokes evenly around the rim. Squeezing the spokes will help gauge the tension, ensure the heads are fully seated, and help relieve stress built up in the spokes.     After squeezing the spokes together, check the tension in the spokes one final time. Most spokes should only be tightened up to 6Nm and the rim I was working on called for 2.2Nm of torque. A spoke torque wrench is the appropriate tool to use to set the final torque of all the spokes, however I didn’t have one on hand and some of you may not either. Instead I based the final spoke tension on how the new spokes felt in relation to a previously laced rim. This method worked okay, but it is always best to use the right tool for the job.   After you’ve finished tightening all the spokes it is never a bad idea to check runout both axially and radially one final time to confirm the rim hasn’t shifted. As long as the spokes were tightened evenly, changes in runout should not be an issue. Once you have checked runout one last time you are all set to install a new rim strip and put on the tire.     I hope you enjoyed this two part series on building and truing rims. Now that you have the info to feel confident building your own wheels from here on out, and are able to save some cash in doing so, go for it!   Just a heads up, you've got only three more days to use the thumpertalk2015 discount code on The Four Stroke Dirt Bike Engine Building Handbook (eBook) and get 20% off. If you love working on your engine and bringing your four stroke to its highest state of tune, then you are going to love the in-depth precision engine building knowledge I am providing for at-home mechanics and experts in this fully illustrated eBook. The eBook comes in PDF format, is sent immediately to your email inbox, where you can read it or print it off, and bring it into your workshop. To grab your copy and use the thumpertalk2015 discount code before it expires, click here.   If you have tips and tricks pertaining to wheel building, I’d enjoy hearing them. Please leave a comment below!   -Paul Olesen
DIY Moto Fix - Empowering And Educating Riders From Garage To Trail

Paul Olesen

Paul Olesen

 

Do You Know How To Properly Inspect a Clutch?

Having a clutch that works correctly is key to being able transfer all the power your engine produces to the rear wheel (or wheels if you're a quad guy/gal). In this post I want to share some key clutch inspection techniques I use and recommend to help ensure your clutch works as it should. These tips are presented in a step by step format and are taken right from my book, The Four Stroke Dirt Bike Engine Building Handbook.   Basket Inspection
Inspect the driven gear which is secured to the basket. Look for damaged gear teeth and other imperfections. Grasp the gear and basket firmly, then try to twist the gear. The gear is secured to the basket either with rivets or fasteners. With use, the rivets or fasteners can loosen causing the gear to become loose. Most baskets use round rubber dampers to locate the gear to the basket, which are sandwiched behind the backing plate. The dampers can wear out and break, which will create excessive play between the gear and basket. Any looseness may have been accompanied by excessive gear noise or rattling sounds when the engine was previously running.     On baskets with loose gears and riveted backing plates the corrective action which will need to be taken is to either replace the basket or drill the rivets out. The idle gear may need to be pressed off in order to remove the backing plate. Once this is done, holes can be tapped and bolts installed which will secure the gear in place. Any rubber dampers that have worn can be replaced with aftermarket options. Check out this article for more details on clutch basket damper replacement: How to repair your clutch basket dampers for less than $30.   Inspect the needle bearing bore surface on the basket next. Run your fingernail across the bore feeling for signs of wear. The bearing surface should be smooth and free of imperfections. If the surface is grooved or worn the basket will need to be replaced.     Inspect the area inside the basket where the large thrust washer resides. Wear should be minimal in this area. If any grooving is present, the needle bearing and spacer the basket rides on may have worn causing the basket to wobble or the pressed in steel insert has backed out, ultimately causing the face of the basket to rub on the edges of the washer.     Check for bent clutch basket fingers on the basket. Then look for grooving on the basket fingers where the clutch discs come in contact with the fingers. Grooving is caused by the clutch discs slamming into the clutch basket fingers. Normally grooving will be more pronounced on the drive side fingers. Grooving is not abnormal and occurs through usage of the clutch.   If any grooving is present, use the end of a pick to evaluate how deep the grooves are. Any grooving that can catch the end of the pick is also likely to be able to catch the edge of the clutch discs. When this happens, the clutch will have difficulty engaging and disengaging. If your bike had clutch disengagement/engagement problems prior to disassembly, basket grooving is the most probable cause.     A file can be used to smooth the grooves so the discs no longer catch, however deep grooving is an indication that the basket is near the end of its life. When filing clutch basket fingers, attempt to remove as little material as possible and remove material evenly from all the fingers.   Some manufacturers provide a specification for the clearance between the clutch disc tang and the basket fingers. This clearance can be measured by temporarily installing a clutch disc into the basket and using a set of lash gauges to check the clearance between the two parts. Both the clutch disc tangs and basket fingers will wear so if the clearance is outside the service limit it may be possible to prolong the life of the basket by installing new clutch discs. This is a short term fix however, and replacing both components at once is advisable.     Bearing/Spacer Inspection
Inspect the clutch hub needle bearing and spacer for signs of wear. The needle bearing will be replaced with a new bearing, but if the spacer is in good condition it will be reused. Check for grooving or concavity along the surface of the spacer where the bearing rotates. While the needle bearing won’t be reused, it can be inspected as well to help confirm any problems associated with the clutch basket or spacer.     Hub Inspection
There are two main areas on the clutch hub which will wear. First, grooving can occur on the splines which locate the clutch plates to the hub. The grooves are a result of normal clutch use and occur when the steel clutch plates rotate back and forth in the spline grooves. Any grooving which catches the end of a pick should be considered problematic. Careful filing to smooth the grooves or hub replacement are the two options available for remedying the issue. The clutch plates must be able to easily slide back and forth along the hub, otherwise clutch disengagement/engagement problems will occur.     The second area susceptible to wear on the clutch hub is at the back face of the hub. This is where the outer clutch disc contacts the hub. When the clutch is engaged, the clutch disc and hub will rotate in unison. However, when the clutch is partially engaged or disengaged, the clutch disc will rub against the face of the hub causing both the hub and disc to wear. Look for uneven wear patterns and indications of how deep the clutch disc has worn into the clutch hub.     If the face of the clutch hub has worn excessively or unevenly, the hub should be replaced.   Pressure Plate Inspection
The interaction between the pressure plate and clutch disc is identical to the situation previously described between the clutch disc and clutch hub. Wear will occur on the face of the pressure plate which contacts the outside clutch disc. Determine the condition of the pressure plate by looking for signs of excessive or uneven wear on the face of the pressure plate.     Disc and Plate Inspection
Both the clutch discs and clutch plates are designed to be wear items which will need replacement from time to time. Thickness and straightness are the primary inspection criteria used to determine if either component requires replacement. If there are any problems with any of the discs or plates replacing them as a set is best.   Clutch Disc and Clutch Plate Inspection
Clutch discs are made out of various compositions of fibrous materials which wear at different rates, while clutch plates are made from steel. Service manuals will specify a minimum thickness that the clutch discs and plates can be. This thickness can easily be measured by using a caliper. Take measurements at three to four locations around the clutch disc or plate to confirm either has not worn unevenly.     Once all the disc and plate thicknesses have been measured, both should be inspected for warpage. This can be done by laying the disc or plate on a surface plate or other flat surface. A set of lash gauges are used to determine any warpage. The service manual should specify a maximum warpage value which is usually around 0.006” (0.15mm). Attempt to insert the 0.006” lash gauge underneath the clutch disc or plate at multiple points. If the feeler gauge slides beneath either of the parts, those parts are warped and should be replaced.     Clutch discs which have been overheated due to excessive clutch fanning by the rider, not only may warp, but also emit an unpleasant stinky burnt smell. If a noticeable smell is present, the discs have overheated and should be replaced. Likewise, clutch plates that have overheated will likely be warped and exhibit discoloration. The discoloration is a sign of excessive heat build up. Once the clutch plates have overheated, the material properties of the plate change, the hardness is reduced, and the plate becomes less wear resistant. This means discolored plates should be replaced.   Lastly, inspect the clutch disc tangs for wear, chipping, or damage. If any tangs are damaged the disc should be replaced.   Clutch Spring Inspection
Over time and due to normal clutch use, the clutch springs will shorten. Clutch spring minimum free length specifications are provided by manufactures and can easily be measured using a caliper.     Clutch springs that are shorter than the minimum spec provided by the manufacturer will not have sufficient spring pressure to keep the clutch from slipping under heavy loads. Any springs at or past their service limits require the replacement of all springs as a set. This way when the new springs are installed, even pressure is applied to the pressure plate.   I hope you enjoyed this passage from my book detailing clutch inspection. If you have additional tips you'd like to share please leave a comment!   If you want more technical DIY dirt bike engine information, learn more about the book on our website or on Amazon. Simply follow the links below!   The Four Stroke Dirt Bike Engine Building Handbook   Amazon Store     Thanks for reading!   -Paul

Paul Olesen

Paul Olesen

 

What Changes In Valve Shim Size Can Tell You About Your Engine

I hope you enjoyed my last post on ice tire studding! The season in my neck of the woods has been a bit short this year and I may be getting back to the dirt sooner rather than later. Nonetheless, Part II, which covers mounting ice tires is now up on my blog. You can view it here: Ice tire mounting.   In today's post I'm going to shift focus back to the engine and talk a little about valve technology. Valve technology and manufacturing techniques have changed substantially from the earlier days of engine development and I want to share with you some information about the current valve technology being implemented in your engines. I also want to discuss one way you can get a feel for how much life is left in your valves. Let’s get started.   The following excerpt is copied directly from my book, The Four Stroke Dirt Bike Engine Building Handbook. If you want to learn more helpful tips, which will bring your maintenance knowledge and engine building skills to the next level, I’d like to invite you to pick up a copy of my book by clicking here. Be sure to use the offer code tt2016 to get 15% off when ordering!   Alright, on to valves shim sizes.   The cylinder head assembly of most engines will wear out before it resorts to telling you it has had enough by catastrophically failing. Diagnosing these wear signs and knowing when it is time to replace components is the key to keeping the cylinder head assembly from failing. Due to the aggressive camshaft profiles, high compression ratios, and high RPMs required to make a lot of power, the valves and seats typically are the first parts to wear out within the cylinder head. Worn valves and seats will cause the engine to become difficult to start, have low compression, and have reduced power.     Modern valves found in dirt bike engines are made from either titanium or stainless steel alloys. Regardless of valve material, modern valve faces are either coated in a variety of anti-wear materials or hardened using various hardening processes. Common examples of trade names you might be familiar with include diamond like coatings (DLC) and black diamond coatings. These coatings are typically harder than the base material of the valve and help the valve resist wear, which occurs from ingesting dirty air and repeatedly contacting the valve seat. Coating and hardening processes are only present at the surface of the valve face. Depending on the type of valve and process used to harden it, the coating thickness can range from as little as 0.0001” (0.003mm) to around 0.003” (0.076mm). An easy way to visualize the thickness of the coating is to pluck a hair from your head and either measure it or feel it between your fingers. Most human hairs are around 0.002” (0.05mm) which should give you a good idea of how thick the coatings used on the valves are.   The important takeaway here is that if the coating is only a few thousandths of an inch thick, the valve can only be adjusted a few thousandths of an inch before it will have worn through the coating. Monitoring the starting valve shim size once the engine has been broken in (or new valves installed) and comparing that size to the shims required the next time the clearances are adjusted is a great way to assess valve health. Normally within the first 3-5 hours of breaking in a new engine the valve shim sizes may change slightly. This is due to the mating of the new valves to the seats and any valve seat creep which may occur. After this occurs and the valves have been shimmed to compensate, usually an adjustment up to around 0.004” (0.10mm) is all that can be done before a valve has worn through its hardened surface. Once this happens the valve face will wear much more quickly and start to wear out the seat as well. This will result in more frequent valve shim intervals and necessitate the need for having the valve seats cut. By paying attention to changes in shim sizes you will be able to approximate when the valves have worn through their hardened surfaces and must be replaced.   Thanks for reading and please leave questions or comments below. I enjoy hearing from you!   Remember you can get 300 pages worth of in-depth dirt bike engine information with The Four Stroke Dirt Bike Engine Building Handbook. Be sure to use discount code tt2016 at checkout to receive 15% off your order!   -Paul   DIYMotoFix.com

Paul Olesen

Paul Olesen

 

What you really need to know about air filter maintenance

Air Filter Maintenance - What You Need To Know
In my last post I shared an account of what happens when dirt gets past the air filter and into an engine. This was a telling tale, however I want to go further and discuss key components of what can be done in terms of maintenance to limit the chances of sucking in dirt. Whether you ride a two-stroke or four-stroke, it makes no difference, the importance of keeping dirt out cannot be overstated.   I want to start off by thanking those that left constructive comments in my previous post. Your insights into filter maintenance are much appreciated and help reinforce what I’m about to share.   How often should I change my air filter?
This depends entirely on the conditions you ride in. Dusty dry conditions will warrant more frequent filter changes than a damp riding environment where dust is non-existent. The amount of dirt accumulation that is acceptable is subjective, but I always err on the safe side. As an example, my filters are blue when freshly oiled and as soon as they start to become blotchy and start to turn color I change them.   Can I change my air filter too often?
Yes and no. I say yes only because every time the filter is removed there is a chance for dirt to enter the engine. A sensible changing regimen decreases the odds of dirt getting into the engine as the filter is removed/installed.   What to Use
I’ve personally been using FFT filter oil, however, there are many great options out there. No Toil’s water based oil system is something I’ve heard good things about and would like to try too. Asking other riders or doing a quick search will certainly turn up more great options as well.   Removing the filter
The main point I want to mention here is to be careful when removing the filter from the airbox so that dirt does not come off the filter or surrounding areas and find its way into the intake. On most bikes, fitting the filter between the subframe is a tight fit and dirt can occasionally come off as the filter is pulled up.     To help prevent this, clean the subframe or any areas the filter is likely to contact prior to removing it. Also watch for dirt accumulation at the top of the filter between the sealing flange and airbox.   Airbox Cleaning
Prior to any cleaning efforts be sure to use an air box cover or stick a clean rag in the intake tract which will help ensure any dirt that is dislodged won’t make its way into the engine.   Filter Cleaning
The correct way to clean a filter depends entirely on the type of oil used. Petroleum based oils will require a two step cleaning process. First a solvent must be used which removes the majority of the dirt. Second, the filter must be cleaned in soapy water and rinsed.   Water based oils only require a one step cleaning process using soapy water or a water based filter cleaner.   Selecting Solvents for Cleaning Away Petroleum Oils
Air filters consist of multiple foam elements which are bonded together chemically with adhesives. Depending on the adhesives used in the filter, certain solvents may or may not react. If a reaction occurs, the joint can break down and the filter can be ruined.   When selecting a solvent, it is always a safe bet to follow the recommendations provided by the filter manufacturers. However, as many will point out through their own experiences, there are several potential solvents that can work in place of the manufacturer’s.   A quick forum search will surely result in an overwhelming number of hits on filter cleaning and potential solvent solutions. I personally use parts washing fluid which I've downgraded from the washer to a bucket.   Cleaning Technique
The biggest tip I can share here is to make sure you only squeeze the filter when cleaning, don’t twist it. Squeezing lessens the likelihood of the glued joints getting damaged.   Filter Oiling
The goal is to get complete uniform saturation without over oiling. This can be done a number of ways and is largely dependent on the method of application (rubbing in by hand, dunking in oil, spray on, etc.).   My preferred method is to dispense oil from a bottle and work it in by hand. I believe this process keeps the amount of excess oil at bay, isn’t too messy, and it’s relatively easy to get good uniform saturation.   Many filters have two stages, a coarse foam filter element good for trapping large particles and a fine element suited for trapping smaller contaminants. Be sure to work oil into both elements.   Remember when working the oil in to be gentle with the filter. Rub and squeeze but don’t twist.     Once the filter is saturated with oil remove any excess by carefully squeezing the filter. Ideally, very little excess oil should get squeezed out, but remember, this is entirely dependent of how generous oil was applied. After excess oil has vacated the filter a nice even thin layer of oil should be visible.   Batch
Filter oiling is a dirty job. No matter how hard I try, oil always seems to end up where I don’t want it. To make things messy less frequently, batch the filter cleaning and oiling process. Buy a few filters, oil them, use them, clean them, and then repeat the process all over again so the task isn’t done as regularly.   Keep the pre-oiled filters in Ziploc bags so that they’re ready to go when you need them.     Greasing the Flange
Is it necessary? I believe the directive to grease the flange of the filter may have originated long ago when the sealing flanges of filters were not predominantly foam. Nowadays whether grease is necessary or not is mostly personal preference accompanied by whether or not the filter cage and airbox seal flat to one another, and how tacky the oil is that is being used. Personally, I still use a waterproof grease on my filter rims, however I’m aware it is probably not necessary in all circumstances.   Installation
Keeping dirt off the freshly oiled filter during installation is the main challenge. There are a few helpful tips I can share for doing this.   First, make sure the bolt is installed in the filter cage! It’s frustrating when you forget it.   Once you’re ready to install the filter I find that rotating the filter 90 degrees to its normal direction so that it can more easily be slipped past the subframe makes things much easier. Once down in the airbox the filter can be rotated into position.     The other option is to use a plastic bag as a shield effectively covering the filter while it is being lowered down. Once in position the bag can be removed.   Wrap Up
I hope you’ve enjoyed my post on air filter maintenance. If you have any questions or comments please share them below!   For those of you interested in all things engine related check out my book, The Four Stroke Dirt Bike Engine Building Handbook for more awesome information. In honor of Independence Day we’re having a two week sale where you can save 15% by entering offer code july4th at checkout if you order before July 17th.     Thanks for reading!   -Paul

Paul Olesen

Paul Olesen

 

What Tools Do You Need To Correctly Rebuild A Dirt Bike Engine?

To continue on our engine rebuild journey I want to discuss tools this week. Use this post as a basic idea of what tools are required to do a complete engine rebuild at home. Now I know a lot of you probably have a pretty good idea of what is required, but I want this to be a quality resource for anyone just starting out and considering working on their own engine. Below I have shared all the tools required to do a full rebuild, top and bottom end, on a Honda CRF450R. Understandably each make and model will differ slightly due to parts, however I believe this example will provide a great overview of what is necessary to complete a highly thorough rebuild. In addition to the list here, I put together an Amazon wishlist of "Engine Rebuilding Tools" that you can check out by clicking HERE. I want to point out that I am in no way affiliated with selling any of these tools nor do I guarantee that you will find the cheapest prices by purchasing tools off of this list. I will take responsibility for any impulse buys and am willing to act as a scapegoat should you have to explain why you spent a load of cash to your significant other. Amazon has a very nice way of bundling all the tools into one place so you can get a feel for the individual prices. I added tools to the wishlist based on my own experience with them (I own a good portion of what's on the wishlist) and looked through user reviews on the tools I don't own. When creating the wishlist I definitely kept budget in mind, but these are not necessarily the cheapest options. This tool list is a good place start if you're looking to add to your toolbox. While some may argue or believe they need Snap-On grade tools, I believe most people can get away with a good economical set of tools. There is no-doubt that mechanics who work with their tools everyday need high quality tools, however the at-home mechanic isn't experiencing the intense workflow of a professional mechanic and will use their tools much less over time. This makes it more economical to buy lower priced tools and replace them slightly more often than the big buck tools. The trick to getting tools you'll be happy with is knowing where to spend a few extra bucks for a quality tool. I believe about 90% of all the tools you need for working on a motorcycle engine can be had pretty reasonably. The remaining 10% is where a little time spent researching good options and spending a little extra money comes into play. The 10% Final assembly tools (torque wrenches), specialty tools, and measurement tools are the three categorizes where you should look for good quality tools. Reassembling an engine or other parts with torque wrenches that are inaccurate can lead to big problems if you end up over tightening bolts, stripping threads, and damaging parts. Not investing in specialty tools which allow you to disassemble and assemble parts correctly can also lead to damaged parts. Finally, precision measurement tools are what determine if your engine components, such as cylinder and cylinder head, are in spec or need to be serviced. Measurement tools are a very special breed of tool. It takes practice to learn how to use them proficiently. If not used properly, these tools can result in inaccurate measurements. If I were just starting out learning how to rebuild engines I would seek the help of a professional machinist or builder to help with the portion of the rebuild where you need to inspect the cylinder and cylinder head. These are two of the most important parts on an engine and incorrectly assessing the condition of these parts can lead to premature failures. For builders just starting out, experience could be gained by measuring less important parts. From there you can work your way up to becoming proficient at measuring the cylinder and head. Quality measurement tools such as those offered by Starrett, Mitutoyo, and other industry leaders, can be extremely expensive for the home mechanic to buy new. There are other options such as buying used or buying brands such as Fowler, Brown and Sharp, or Anytime Tools to name a few. In my experiences the quality offered by the lower cost brands has been quite good and when I have compared some of my cheaper measurement tools to the industry standard brands they have done very well. Like all tools, measurement tools are an investment and determining if you'll get enough use out of them to warrant the cost must be determined on an individual basis. For folks just starting out I think having a a nice pair of calipers, 0-1" and 0-2" micrometers, and a set of lash gauges will do your rebuild justice. Do you have tools you want to recommend? Have something to add? Please leave a comment below. For those who have been interested, our Honda CRF450 Bottom End Full Engine Rebuild Video Manual has launched. You can check out all the details, including a preview of the video manual HERE. Moto Mind - Empowering and Educating Riders From Garage to Trail http://www.DIYMotoFix.com

Paul Olesen

Paul Olesen

 

Tips on Buying a Used Motorcycle

TIPS ON BUYING THE PERFECT USED BIKE How many of you have bought your fair share of used bikes only to discover the moment you get it home that something is wrong with it? I have bought and sold a hefty amount of different types of vehicles over the years and recently started reflecting on some of my experiences. I have bought bikes that have run well, did not run at all, were partly assembled, or were complete basket cases. Sometimes there have been great deals and sometimes there have been total lemons. Occasionally I have even purchased bikes sight unseen and put my good faith in others to collect them for me. Has some of my behavior been risky when buying a used bike? Absolutely, but because of those experiences a lot of hard earned knowledge has come my way. With all the variables that get thrown into purchasing a used bike wouldn’t it be great if there was a way to increase your chances of avoiding a lemon? Over a month ago I started compiling all my used motorcycle buying advice to share with you. Now I know most of you are experts at buying used bikes, but these guides are great because it puts everything conveniently in one place, not to mention a printable checklist you can take with in your back pocket to reference in case you forget a few things. I began by writing down everything I considered vital when purchasing a used bike. Beginning with the research phase, I gave pointers on what to look into - prior to even browsing through any ads. Next I organized all the different things that are worthwhile to look over on the bike itself. In conjunction with that, I wrote down all the questions I think are important to ask the seller. Being allowed to test ride the bike is a huge thing for me also, so I went over all the different test procedures I use when test riding a potential bike. Last, but certainly not least, I included my tactics and tips when negotiating with the seller. These tips aim at the end result of hopefully heading home with a fantastic used bike in tow. After all this writing I ended up with two 30+ page buyer’s guides - one for dirt bikes and one for street motorcycles. These guides are the most thorough and detailed when it comes to purchasing a used bike I have found. I want to share eight of what I consider the top tips with all of you in my blog and ask that you download whichever free guide you need to learn the rest as there is just way too much information to post here. KNOW WHAT YOU WANT - RESEARCH MAKES & MODELS Thoroughly researching different makes and models will go a long way to ensure you get the bike you want. Familiarize yourself with the bikes you are interested in by researching and reading reviews on the particular makes and models you're interested in. By reading the reviews you will be able to gain a better understanding of what sort of performance you can expect from particular models, their shortcomings, and some things you can do to improve these bikes. CHECK THE VIN NUMBER Look on the frame of the bike for the VIN number to ensure that the bike is not stolen. If the VIN number is scratched off or the sticker has been removed, this is an indication that somewhere within the history of the bike it may have been stolen. If you have any suspicion that the bike is not clean, contact your local authorities and have them run a VIN number check. Refrain from exchanging any money until the the history of the bike is cleared. FEEL THE MOTOR Carefully feel near the engine for heat radiating off the engine to determine if the engine has been started prior to your visit. If the motor is warm it could indicate that the bike does not start easily when it is cold and the seller is trying to mask an issue with the carburetor or fuel injection system. If it is an older bike, a potential fix would be to clean and inspect the carburetor. If it is a fuel injected bike, there could be issues with the injectors, the fuel pump, the ECU, or the ignition system. CHECK HOW CLEAN THE MOTORCYCLE AND THE ENGINE ARE Often times if there is a problem or the motor is leaking, the seller will power wash the motor to hide the leak. If the motor or bike is suspiciously clean, when the seller runs the motor for you, double check around the engine for leaks that may appear. ASK THE SELLER WHY THEY ARE SELLING? This is a great ice breaker. This questions gives perspective into the seller’s motivation and reasons for selling. It also may give a glimpse into potential issues the bike may be having. HOW MANY MILES ARE ON THE BIKE AND WHAT HAS BEEN SERVICED? The mileage on a bike can be used as a very rough gauge to determine where it is at in its life however nowadays motorcycles are designed to perform well and not require a great deal of service work even with high mileage. How well the owner has taken care of the bike, the type of riding they did, and the conditions in which it was stored are all better factors for assessing where it is at in its life cycle. Street bikes typically require service after predetermined mileage intervals established by the motorcycle manufacturer. These services may include valve clearance checks, oil and filter changes, and clutch maintenance. This question will help you gauge when and how much upcoming service work may be required. In most cases street bike engines will last a long time and not require much internal engine work if the engine is routinely serviced and basic maintenance is performed. By familiarizing yourself with some of the routine maintenance tasks for the make and model you are interested in you can gauge the frequency and scope of work which is considered routine maintenance and compare this to what the seller tells you. Keep in mind if you are looking at bikes that have been raced or are of the single cylinder variety more maintenance may be required to keep them in top shape. LET THE ENGINE WARM UP & LISTEN TO IT IDLE Allow the engine to come up to operating temperature, this usually takes a few minutes of idling. Most bike are equipped with a coolant temperature gauge which you can reference to see how warm the engine is. Listen as the engine runs for how well the bike idles. The bike should have a nice consistent idle and the motor shouldn’t be hunting or surging. Assuming the bike is carbureted and does not idle, it is likely that the carburetor needs servicing or something is out of adjustment. If the bike is fuel injected and does not idle, there could be an issue with the fuel map, pump, or injector. SHIFT THROUGH ALL THE GEARS Feel with your foot how easily the bike shifts into the next gear. You should be able to feel if the gears kick back out or do not engage easily. If the bike jumps out of gear or does not shift well, there could be problems with the gearbox. Pay special attention to the shift from 1st to 2nd gear since this is the shift that requires the biggest stroke to engage (since neutral is between them) and usually wears out first. Typical problems may include rounded gear dogs, bent shift forks, or worn shift forks. Remember if any of these problems exist you will have to split the crankcases to remedy the problem (unless the engine utilizes a cassette style gearbox or has a separate transmission). Be sure to shift through all the gears at least a few times to make sure any problems that arise are repeatable and predictable. This will help rule out any user error where the rider did not shift fully. If you like the tips shared thus far and want to learn more about navigating the slippery slopes of buying a used bike, I would encourage you to download the free guide you need, whether it is dirt or pavement. The guides come in the form of a downloadable PDF, ready to be printed and kept forever. The Buyer’s Guides also include a checklist that you can bring along and reference as you proceed through all the steps of buying a used bike. The checklist is incredibly useful when it comes to looking over the bike and inspecting individual components. I know my adrenaline goes wild when picking up a new bike and I run the risk of skipping over one or two important things, so the checklist will ensure you do a thorough job. Just click the link below to go to the downloads! Grab Your Free Used Dirt Bike or Motorcycle Buying Guide Do you have any tips that I left out of the guides? If so, post them in the comments section so everyone can benefit from your experiences! Moto Mind - Empowering and Educating Riders from Garage to Trail P.S. If you haven't subscribed to my blog yet be sure to click the "Follow this Blog" button at the right of the page!  

Paul Olesen

Paul Olesen

 

Piston Ring End Gap and Why You Should Care

I hope all of you in the Thumper Talk community are doing well and have benefited from my last blog post. This week I want to hit on a topic that ties in closely with last week’s topic on warming up the engine and the concept of thermal expansion. Piston Ring End Gap and Why it Matters Let’s talk piston rings. The rings’ primary function is to seal the combustion chamber and keep the pressure that builds on the compression stroke from escaping. Secondly, the rings provide a means for heat to transfer from the piston to the cylinder wall and then to the cooling system. Lastly, on four-stroke engines the rings act as a seal between the combustion chamber and the engine oil. Often times a special oil control ring is used to perform this function and is located furthest from the piston crown. Most of you are probably familiar with the practice of checking piston ring end gap when assembling an engine. What I want to share with you is why it is important to check ring end gap. Checking ring end gap when putting a new engine together or rebuilding an old one is critical because it will determine whether your engine runs flawlessly for countless hours or if you just wasted a whole bunch of money on a bunch of parts that are about to become scrap the first time you run the engine hard. Let me share a quick story with you. The first time I assembled my Kawasaki H2 two-stroke triple engine I couldn’t wait to hear it run. It was tempting to skip all the steps I would call critical to the success of a good engine build, but I’m sure glad I didn’t. First, I noticed that my gearbox was improperly shimmed by the company that back cut my gears. Next, I found that the right hand piston came with the wrong rings! I tried assembling the rings onto the piston and noticed that the gap was almost four times as much as the spec’d value given by the piston and ring manufacturer. Had I decided to run with the rings that had that excessive end gap it probably would not have resulted in a failure. The right cylinder simply would have been down on power since most of the gas being compressed could escape and the cylinder would have low compression. Now what if the situation was opposite what I just described? What if the rings had no end gap? Well, the outcome would have been much worse. Running your engine with too little end gap is a recipe for disaster. It’s time to revisit what I said last week about thermal expansion and how parts expand at different rates. If at room temperature there was no gap between the ends of the piston rings, what would happen when the rings’ temperature was elevated to 180°C? The ring would have no room to expand as it heated up and it would get tight to the cylinder bore, start to want to stick, scuff the cylinder bore, and wreak havoc on your entire engine! This example and explanation is the reason it is so critical to check end gap of the piston rings when assembling a new engine. My advice when setting end gap would be to follow the manufacturer’s recommendations for end gap for their given product. The only time it might be necessary to deviate from their recommendations would be for race applications where more heat is generated than in a normal application. When in doubt, more end gap is always better than too little. Most of you are aware that there are at least two sealing rings in a piston assembly and by now perhaps some of you are wondering if the end gap of each ring should be set the same. In my opinion it is best to set the second ring end gap to be slightly more than the first. The reason for this is to limit the possibility of pressure building up under the top ring. If pressure builds up under the top ring it increases the chance of the top ring fluttering which should be avoided at all costs. By having the second ring’s gap a little looser than the first, any combustion pressure that gets between the two rings has an easier time exiting. For those of you who don’t mind a little math, here is a nice example. How exactly do the manufacturer’s determine the end gap that should be run? Let’s say the rule of thumb might be 0.003” of end gap per inch of cylinder bore for a particular application. Well who the heck decided on 0.003” per inch of bore and why? Let’s assume the following for the sake of simplicity: Cylinder crown temp = 300°C Piston ring temp = 180°C Cylinder liner temp = 100°C The formula for linear expansion is: ∆L = α x D x ∆T where: ∆L = Change in length of the piston ring α = coefficient of thermal expansion (in this case steel = 0.000012m/m°C) D = original diameter of the cylinder ∆T = Change in temperature α = 0.000012m/m°C D = Let’s assume the diameter to be equal to 1”. ∆T = 180°C - 100°C (difference between the liner and ring) Now it all gets put into the equation and solved. ∆L = 0.000012m/m°C x 1 x 80°C ∆L = 0.003015 inches So in our example, using temperatures fairly close to actual engine temperatures, we see that the ring will expand roughly 0.003 of an inch per 1 inch of cylinder bore. Hopefully this gives you a better idea of why the manufacturers specify the end gaps that they do. Moto Mind - Empowering and Educating Riders from Garage to Trail If you'd like to follow my blog, click the "follow this blog" button in the upper right. I'd love to have you.

Paul Olesen

Paul Olesen

 

Is A Piston Upgrade Right For You and Your Four-Stroke?

This month I wanted to share an exert from the Race and Performance Engine Building chapter in my book, The Four Stroke Dirt Bike Engine Building Handbook. If you've been wondering how high compression pistons work and if they are right for your application, read on!   Piston upgrades are normally considered when changing the compression ratio is desired or larger valves are installed. In both instances the shape of the piston is altered either to reduce the volume in the combustion chamber or to allocate additional room for larger valve pockets.   The compression ratio defines how much the original air/fuel mixture which was sucked into the engine is compressed. The following equation shows how an engine’s compression ratio can be calculated.     The swept volume is the volume that the piston displaces as it moves through its stroke. Mathematically this volume can be determined using the following equation.     The clearance volume is the volume of the combustion chamber when the piston is at top dead center (TDC). While manufacturers specify what the compression ratio should be, due to subtleties in manufacturing, parts vary slightly from engine to engine so finding the exact clearance volume of your engine actually requires measuring the clearance volume.   Undoubtedly you have probably heard that raising the compression ratio will increase the power of an engine. This is definitely true, however you should be aware of the other consequences that come along with this.   The more the air/fuel mixture can be compressed before it is combusted, the more energy which can be extracted from it. The reason for this is due to thermodynamic laws. In summary, the temperature difference between the combusted mixture when it is hottest and coolest determines the power and efficiency of the engine. The hottest point of the mixture will arrive shortly after the mixture has been ignited and the coolest point will occur around the point where the exhaust valves open. Since the temperature of a gas increases as its volume decreases, it is easy to see how increasing the compression ratio increases the overall combustion temperature. Something less obvious is that because the gases are compressed more, they will expand more and actually be cooler by the time the exhaust valves open.
  If increasing the temperature of the compressed mixture is good, you might be wondering what keeps us from raising it higher and higher. Detonation, which is a by product of the additional heat and pressure in the combustion chamber, is the main reason the compression ratio can’t be increased beyond a certain point. Detonation occurs after the spark plug has ignited the air/fuel mixture. Normally once the spark has ignited the mixture, the flame will propagate outwards from the spark plug evenly in all directions. When detonation occurs some of the remaining air/fuel mixture situated towards the edges of the combustion chamber spontaneously combusts before the flame reaches it. When this happens a large spike in combustion pressure occurs. If severe enough detonation can cause engine damage in the form of pitting on the piston crown, broken ring lands, and scuffing of the piston from overheating.   To combat detonation there are a few different parameters which can be tweaked to help alleviate the problem. The air/fuel ratio can be altered along with the engine’s ignition timing to change the peak combustion temperatures, a fuel with a higher octane rating can be used which will be more resistant to detonation, and upgrades to the cooling system can be carried out to help keep the combustion chamber cooler.   Along with increasing the likelihood of detonation as a result of increasing the compression ratio, the engine will also produce more heat. The cooling system must absorb this additional heat and be able to adequately cool the engine, otherwise overheating and detonation may be problematic. Radiator size, thickness, and the speeds at which you ride at all play a big role in how efficiently the cooling system operates.   Now that you have an understanding of how high compression pistons affect performance, you can consider if this will be a good modification for you. Aftermarket pistons are usually offered in a few different compression ratio increases. You will want to look closely to see if any high octane fuels will be required to use in conjunction with the piston and if any cooling system improvements are necessary.   For racers looking to extract all the power from their bike, adding a high compression piston is one of the things that will be necessary. If you do a lot of tight woods riding, hare scramble racing, or enduros where low speeds are the norm, you may want to shy away from raising the compression ratio as the cooling system will have difficulty dealing with the increased heat at low speeds where airflow is limited.   I hope you enjoyed this excerpt on piston modifications and how they affect an engine. If you liked this write up and are interested in learning more about performance options and four stroke engine building, pick up a copy of my book. Right now the book is on sale at 20% off our list price when you order within the next two weeks.   You can grab your discounted copy off our site here: The Four Stroke Dirt Bike Engine Building Handbook Or on Amazon: Amazon Book Store     Thanks for reading and have a great week!   -Paul

Paul Olesen

Paul Olesen

 

Who the Heck is Paul Olesen?

Who the Heck is Paul Olesen and Why is he Writing for Thumper Talk? I’m really excited at the opportunity to start blogging because I’m finally going to have an outlet to express my passion for picking flowers, going for walks, and singing songs. I can’t imagine anything more exciting than doing these three things except... maybe, just maybe, riding motorcycles. On second thought, riding motorcycles and figuring out how engines work is definitely much more thought provoking and certainly what I came here to discuss... so lets get started! Most of you are probably wondering who the heck I am and what am I going to talk about. By day I’m a powertrain engineer at an American sportbike manufacturer where I work on and oversee multiple facets of engine development and production. At night I focus on my personal projects, hobbies, family, and whatever else might interest me. Since the age of 18 I’ve lived and breathed motorcycles. I’ve raced multiple disciplines (everything from road, ice, trials, salt flats, and hare scrambles), built my own racing bike, designed my own engines, modified a handful of bikes, and most importantly- made a whole lot of mistakes. These experiences, failures included, have put me in a position to teach you a few new things or at least give you an interesting read. My powersports story started at a young age, however thanks to parental restrictions I was never able to own a bike until I was 18. Once 18 hit, I promptly bought a 1984 Honda Nighthawk 700 from my high school. The bike had been donated by a member of the local community and I had my eye on it for years as I watched students try unsuccessfully to make it run right. Thanks to my never-ending curiosity, that bike very quickly got rebuilt, and to the dismay of my parents, it got ridden a hell of a lot. Shortly thereafter I graduated high school and then attended the University of Minnesota, where I was slated to follow in my father’s footsteps and become a dentist. I don’t recall too many times where I had actually thought that this career path was going to become a reality, so naturally my interest in higher education dwindled at an alarming rate. Simultaneously my interest in motorcycles was at an all time high. I was fascinated by the old Kawasaki two-stroke triples. I had never before seen a two-stroke in a motorcycle and their simplicity, light weight, and abundance of power drew me to them. In a twist of Craigslist-fate a deal for a pair of 1975 Kawasaki H2s popped up in Dallas. Before I could fully rationalize the consequences of skipping an exam, I was on my way with a friend to pick these basket cases up. On my way down to Dallas it hit me that without knowing what I wanted to do with my life, continuing going to school was pointless. I promptly quit two years into my college education, yet again much to my parents’ dismay. I had always made money running a painting business in the summer, so I did that for awhile to make ends meet. While painting has never been a glamorous business it was quite profitable and an important part of my life as it taught me the basics of running a business, allowed me the freedom to set my own schedule, and I learned how to deal with and manage people. Restored 1984 Honda Nighthawk 700 and Restored 1975 Kawasaki H2 The following year my parents ordered me back to school, this time to give engineering a try. I felt like a fish out of water. The idea of being stuck in Minneapolis for another four years brought upon visions of offing myself once and for all. A week in- I quit. I knew I needed a plan if I was going to break the news to my parents. Over the weekend I put on my big-boy pants and started searching for something that I might actually want to do with my life. Low and behold- if you Google “motorcycle engineering” a couple programs pop up in the United Kingdom. That was it, suddenly I was staring my future right in the face, a future that I actually wanted to pursue. Somehow I convinced my parents that going to Wales and attending Swansea Metropolitan University was a good idea, I applied, and got accepted shortly after. Finally I was going to go learn about something I actually wanted to, travel the world, and get a degree in motorcycle engineering. The move to Wales was exhilarating and things really started to take off for me once I began my studies. The structure of the program, the way in which the coursework was carried out, and class sizes were all a lot different than I had expected- but in a good way. The first year was a cakewalk, but it allowed me ample time to learn CAD programs, design a couple fictitious bikes, make friends, and enjoy the Welsh countryside. Towards the end of the year I decided I would design and build my own motorcycle, which I would then intend on racing in the Central Road Racing Association’s club racing events at Brainerd International Raceway in Minnesota. To keep costs down and the project manageable, I decided to build a super mono powered by a Kawasaki KX500 two stroke engine. Initial Chassis Layout My first summer back home I promptly ordered materials for the project and got back to work running my painting business to fund it. The only problem was that I had no mill, no lathe, no pipe bender, and no TIG welder- nor did I know a lot about using any of these aforementioned tools. Suddenly it hit me, there was going to be a steep learning curve. After befriending some locals who were enthused about my ambitious project as I was, in one fell swoop I procured the rights to use all the equipment I required at the odd hours I was intending on working on this bike. It was as if the universe had aligned for the things I had wanted all along as soon as I started asking for them. Quickly I got the jigs made for the frame and swingarm, enlisted the help of my father to work on the fiberglass components, and devised a plan to try and extract more power out of the engine. The biggest hold up that summer was having to teach myself how to weld. That exercise took roughly a month of practice on thin walled tubing and a hefty sized chunk of my own melted skin before I felt proficient to proceed to tackle a real frame. Fortunately, or unfortunately depending on how you look at it, I cocked up the frame design by trusting a friend’s engine model. My first go around at a frame didn’t end up fitting anything, but I got plenty of extra welding practice! By the end of summer the bike was 85 percent complete and I was able to finish the rest of it up over the Christmas and Easter breaks. Super Mono Construction My second year of school was much more engaging academically and focused a lot more on the powertrain side of things which was great. I learned all sorts of useful things to help me along with my race bike build and it was great to be so close to people that could answer some of my questions from a professional standpoint. My first test ride over Easter break came late one evening and to my dismay, it was a disappointing affair. I came back from the ride and my hands and butt were numb from all the engine vibration. Half the bike had rattled loose and the other half the hardware was completely missing! My first real world encounter with engine balancing was about to take place. Much to my dismay, simply changing the balance of the crankshaft did not in fact move the vibration to a more tolerable direction. I needed another solution. After much problem solving, I decided to try and graft on a counter balance assembly I designed to cancel out some of the forces that lead to engine vibration. This proved to be a difficult task with my amateur machining skills, but through much trial and error I managed and the balancer worked! Finishing up the balancer assembly After my second year of school I was offered a job at S & S Cycle for the summer as an engineer. This was great since I got to hang out/pester a lot of smart folks to help me with my race bike project. I learned a lot about machining, manufacturing, and engineering processes at S & S, plus the people there were awesome. My proudest moment while working at S & S was designing and building the land speed fairing for their Bonneville Salt Flats racing bike. This was a time consuming and messy affair, but it paid off when we took the bike out to Bonneville and set four land speed records! Once work was finished for the day, more often than not I went over to my bosses house. He had a decent size shop with a dyno, a hefty amount of tools, and the usual machining equipment- all the things I was requiring to make my world go round. Towards the end of my second year of school I had designed a fuel injection system which I was adamant about implementing onto my bike. That whole summer I spent my time incorporating the system into the engine and learned how to tune the engine on the dyno. By the end of summer my bike was ridable, and I was spending more and more time out on the road test riding. I had hoped to take it to the track for the final race of the year, but other engine problems cropped up and I, along with the bike, ended up staying home. My third and final year proved to be the most time consuming, educational, and one of the most exciting. As part of my degree, I was required to come up with a major project to work on and complete throughout the year. Seeing as my race bike needed a new engine, I began figuring out how to design a new single cylinder two-stroke which would incorporate all the beneficial things that I had learned over the past summer testing the KX500 engine. I settled on designing a 400cc single cylinder counter balanced engine that would use as many common parts as possible with a current production dirt bike transmission. Due to the fact that we actually had a couple Honda CRF450 bikes in the school’s workshop, and parts were cheap and cheerful, I decided to use the gearbox along with a few other parts from that engine. The rest of the engine I designed from the ground up. By the end of my third year I was calling my friends at S & S to help me out with some 3D printing so I could test fit the engine into my frame and the CRF frame. As most almost graduated grads, I was nearing the time where I needed a job, and I didn’t have any spare money to spend on having parts made so the 400cc single project had to be put on hold. 400cc prototype test fitment Job hunting proved to be an interesting time in my life, and even though I didn’t necessarily want all the jobs I applied to, I learned an awful lot through the interview process. I was able to see how companies were run, what real world engineers did, and how engineering roles were divided. Very quickly I began to determine what I did or didn’t want in a workplace and I began to wonder what my future might have in store for me. What also fascinated me was touring all of these companies’ facilities and seeing how the machine shops, engine build areas, dynos, and engineering departments were set up. One of the places I toured that piqued my curiosity the most was Mercedes AMG in the United Kingdom where the Mercedes Formula I engines are designed. I ended up going there twice for interviews and getting a job offer to work there, but thanks to work visa restrictions I was never able to secure the offer since the regulations tightened up after 2012. At that point there was really only one company in America where I thought my skill set and personality would be a good match, and that was at an American sportbike company. I had applied at the sportbike company which I was interested in in the fall of my final year and finally after four months of patiently waiting, I had heard something. An interview was arranged so I came home, loaded up my bike and prototype engine in the back of my van, and set out to East Troy. At the end of the day, after all their questions were answered, it was quite satisfying rolling out my hand built race bike in the sportbike company’s parking lot to show all the interviewing staff what I had done. The interview staff had never had another candidate who built and brought a rolling resume before and they were thoroughly impressed. Right then I realized my persistence at building my own bike had paid off and was largely responsible for landing me two jobs a lot of people dream of. I was brought on as a powertrain engineer in the fall and this is where I currently reside. Throughout my career I have continued to meet wonderful people, learn new things, and further my knowledge of two wheeled vehicles. I hope in a small way my exploits, triumphs, and failures will all be valuable lessons. Paul If you'd like to follow my blog, click the "follow this blog" button in the upper right. I'd love to have you.

Paul Olesen

Paul Olesen

 

Do You Know The Importance of Tightening Techniques?

I hope you’re all enjoying the fall weather. For those of you in northern states, I hope that you’re getting in some end of season riding. This month I want to touch on bolted joints and the importance of adhering to tightening techniques outlined in your model’s service manual.   How A Clamped Joint Works
I’m going to discuss the importance of criss-cross patterns, tightening sequences, incremental steps, and joint lubrication but first I want to explain how a bolted joint works. As a bolt is tightened to secure a pair of parts, the bolt will stretch a very small amount. The stretch in the bolt creates tension or preload in the joint which is the force that keeps the joint together. The amount of preload created is dependent on bolt size, bolt material, the torque applied, and the friction between the threads. There are additional variables, however a discussion on bolt engineering would be very long and not all that exciting! As long as you understand the basics for engine building you can begin to appreciate the importance of correctly tightening fasteners.   As you are well aware, an engine consists of many parts fastened together. What you may not consider as much is that the majority of these parts are fastened by more than one fastener. This means that how much you tighten/preload one fastener will have an effect on the surrounding fasteners. This interaction between the fasteners begins to shed light on why tightening sequences are so important.   The evenness of the preload across the bolts securing a part can affect part life. Warpage can occur in parts which are improperly tightened, ultimately rendering the part useless. A prime example of a part that can warp is a four-stroke cylinder head. If the bolts are unevenly tightened over time, the cylinder head can become permanently distorted. Gasket sealing problems can also occur from improper preloading of bolts across a part. In order for a gasket to seal it must be evenly compressed. If one area of a gasket is highly compressed and tensioned while another area is not, the gasket can easily leak through the low tensioned area. In the case of plain bearing bores, such as the cam cap, uneven preloading may cause the bearing bore to distort. As a result the cam may become difficult to turn. Or if run, the cam bearing bore will wear unevenly and in severe cases the cam could seize.   While ensuring bolt preload is even can be a problem there are three tightening techniques that virtually eliminate the issue. If you’ve been building engines for any length of time you’ve probably already been utilizing these techniques. Hopefully now you may have a better understanding of why the service manual instructs you to tighten parts a specific way.   Criss-Cross Patterns
Criss-cross patterns are called out when tightening or loosening parts with a simple square pattern or circular bolt pattern. These basic patterns have been around for a very long time and are a proven method for evenly distributing clamping load across a part. Most cylinder heads will utilize this type of clamping pattern.

Tightening Sequences
For more complex bolt patterns, such as those found on cam carriers and crankcases, the manufacturer will usually identify a specific sequence for tightening and loosening the fasteners. This sequence is based on testing and the past experiences of the manufacturer.     Incremental Steps
Highly torqued bolts, such as those found on the cylinder head, are almost always tightened and loosened in incremental steps. An incremental tightening sequence consists of torquing all the fasteners to a specific torque value, then increasing the torque and tightening again, and finally arriving at the final torque value. This sequence is typically performed in two to three steps.   Here’s something important to keep in mind regarding incremental steps! When torquing bolts in steps the change in torque between the steps must be large enough to induce bolt movement. For example if a bolt was torqued to 35Nm at the first step and the second step was 38Nm this would not be enough of a change to make the bolt move at the second step. The torque wrench would not overcome the friction of the stationary bolt and would hit 38Nm before the bolt even moves. As a rule of thumb incremental changes should be no less than 5Nm and if possible should be greater.   Lubrication
For highly torqued fasteners often times the service manual will specify that the threads of the fastener must be lubricated. The lubricant can be as simple as fresh engine oil or a specifically formulated thread lubricant product.     Adhering to any lubrication guidelines is of utmost importance. Since we most commonly measure torque to determine whether a bolt has been tightened/preloaded enough any change in the amount of force required to turn the bolt will influence the resulting bolt preload for a given torque value. The force required to turn a bolt is partially dependent on the amount of friction in the joint. If we had two identical fasteners where one was lubricated and the other was not, and we set the torque wrench to the same value for each, then both were tightened, the resulting bolt preload would be different between the two. Due to the reduced friction in the lubricated joint the bolt would stretch more and the preload in the joint would be higher at the specified torque wrench setting than the unlubricated joint. Depending on the criticality of the joint this can be a really big deal! It also shows why in some applications (think two piece conrods) directly measuring bolt stretch is a more accurate means of determining bolt preload.   I hope you enjoyed this quick summary of tightening techniques and their importance! If you have tips of your own you’d like to share or other pearls of wisdom please leave a comment.   For those of you interested in more engine building knowledge check out my book, The Four Stroke Dirt Bike Engine Building Handbook. You’ll find more detailed and comprehensive info on engine building there. Simply follow the links below. Thanks for reading and have a great week!   -Paul     The Four Stroke Dirt Bike Engine Building Handbook   Available on Amazon

Paul Olesen

Paul Olesen

 

How To Properly Replace And Install Spokes On A Dirt Bike Wheel

How many of you become disheartened when spokes break, bend, or a rim becomes permanently damaged necessitating a rebuild of the wheel? I know a lot of people think rim building is a black art and are willing to shell out serious dough to avoid the job altogether. This week I want to debunk the black art of wheel building and provide you with an overview of the process, allowing you to take on your next wheel build yourself. Next week, I’ll cover the second half of the project by showing you how to true the wheel.   As you can see I have a great example of a wheel assembly that is way past its prime. The spokes are bent, loose, and the nipples are mostly all stuck. On top of that, the rim is cracked in a couple spots necessitating further repairs.     Before getting started disassembling the wheel, measure the distance from the rim to the ground. When the wheel is built the rim will need to be blocked up at approximately this height. Blocking the rim up will make the wheel much easier to assemble.     The spokes will be offset from one another. Often times this offset necessitates the use of different length spokes. The spoke kit I received came with two different length spokes and there was no indication of which went where. If there are no instructions provided with your spoke kit and your wheel features spokes of different lengths you will need to determine the correct layout of the spokes. This can easily be done by removing two of the old spokes, measuring them, noting their lengths, and positions.     Once you have determined the spoke length you can go to town cutting the rest of the spokes out of the rim using a cutting wheel or other suitable tool.     Remove all the old spokes, then closely inspect the rim for damage. On my rim I had two nice size cracks I had to deal with.     Once the rim has been replaced or repaired, preparations for lacing can begin. Since the wheel will be exposed to dirt, mud, water, and whatever else nature throws at it, I like to coat all my spokes with anti-seize before assembly. The anti-seize will provide a little extra protection against corrosion and help keep the spokes turning freely for a long time.  
  Separate the spokes according to their lengths so that there is no confusion during assembly.     Next, center the hub and block up the rim. Refer back to the measurement you took to establish the correct block height. As long as the rim is not offset to one side or the other it will not make a difference whether you start with the sprocket or brake side.     The outside spokes will be laced first. If you try the inside route you will quickly find that maneuvering the outside spokes into position won’t be possible. Simply install a spoke into its corresponding hole in the hub then align the spoke with its corresponding hole in the rim. The rim may require some rotating to align the spoke with the correct hole in the rim, however it will be glaringly obvious where the spoke must go since the holes in the rim are all angled.     As the spokes are installed, thread on nipples to retain the spokes. Only engage a few threads as you install the nipples. Keeping the rim loose will allow all the spokes to be installed easier as you go.   Once all the outside spokes have been laced in one side, lace all the inside spokes on that side. Don’t be afraid to pull the rim a little bit from side to side to help generate enough clearance so that the end of the spoke can easily pass through the hole in the rim. The rim may also have to be moved up and down a little bit to help center the spoke.     Next, flip the wheel over and begin lacing all the outside spokes on the remaining side. Pulling the rim from side to side and up and down will be necessary to get all the spokes aligned with their respective holes. By the time you are finished lacing you should have a nice fresh wheel assembly.     A good way to check to make sure the spokes have been installed correctly is to compare the thread engagement on each spoke. With all the nipples tightened only a few turns the remaining threads showing on the spokes should be about the same. If the remaining thread length is vastly different between the inner and outer spokes there is a good chance the spokes have been installed incorrectly. If this is the case, the longer spokes will need to go where the shorter ones currently reside to even things out. If this isn’t done, there is a good chance some of the spokes will run out of threads when the spokes are tightened.     After the wheel has been laced, the nipples on all the spokes will need to be tightened. Tightening of the nipples should be done evenly and gradually. An even pattern can be used to tighten the spokes so that the rim does not become offset radially in one direction. Most wheels either feature 32 or 36 spokes. Every 4th spoke can be tensioned to create an even 8 or 9 step tightening pattern. Once this pattern is completed, the next spoke in the sequence can be tightened and the whole process repeated until you have worked through all the spokes. In the picture below all the red arrowed spokes are tightened first, followed by the greens, then the yellows, and finally the blues.     As the nipples are tightened, checking for evenness among the remaining threads is a nice way to gauge symmetry. You may find that there are small differences between the inner and outer spokes in relation to the remaining threads left on them. Instead of comparing the inner and outer spoke threads to one another, only compare similar length spokes as you work. The more care you take to ensure the spokes are tensioned evenly now, the less work it will be to true the rim later on.     Check to make sure that the heads of the spokes fully seat in their holes in the hub. Some heads may get hung up and will require a tap with a punch and hammer to seat them. Relying on the nipple to pull the head into position doesn’t always work well.     Another sign that the job has been done properly is that the spokes will not pass through the ends of the nipples.     At this point you should have a rim that feels tight, is tensioned evenly, and is ready for truing. Check back next week for a write up on the truing process!   If you found this post beneficial and enjoy tackling projects yourself, you may find my eBook, The Four Stroke Dirt Bike Engine Building Handbook a great read. The book is packed full of in-depth precision engine building knowledge, a detailed overview of performance part selection, and many photographic examples which outline what to look for in problematic parts during a build. The eBook comes in PDF format, is sent immediately to your email inbox, where you can read it or print it off and bring it into your workshop. Right now we have an awesome deal running where all website visitors get 20% off when they enter the discount code thumpertalk2015 before purchasing. To learn more about the book, check out the Table of Contents, and read some testimonials, click here.   Do you have any helpful tips you want to add? Please leave a comment below and share your experiences!

Paul Olesen

Paul Olesen

 

How Do You Keep Track of Where Bolts Go During a Rebuild?

Alright guys, this week I just want to share a short and simple tip with you on how to stay more organized during an engine build.   When it comes to major engine maintenance or repairs, usually the engine covers have to come off or the crankcases must be split. The covers and cases are almost always retained using different length bolts. The repercussions of installing the bolts in the wrong order upon reassembly can be very damaging. This is especially true if you install a bolt that is too short for its location and only a couple of threads engage, ultimately stripping the threads when you tighten the bolt.   So what’s an easy way to keep track of cover or case bolts that are arranged in a pattern of different lengths?   My favorite way to organize these bolts is to take a thin piece of cardboard (think cereal box thickness) and then slit the approximate bolt pattern into the cardboard so that the bolts cannot get mixed up. A picture is worth a thousand words so check out the one below. You need not be an artist to apply this tip, simply slit the pattern, add a couple reference points and you’re done!     Do you have any organizational tips you’d like to share? Leave a comment below because I'd love to hear about them!   If you are looking for more helpful tips and engine building info, feel free to check out my book, The Four Stroke Dirt Bike Engine Building Handbook. You’ll find 301 pages filled with crucial and down-to-earth four-stroke engine building knowledge. You've got one more week left to use the offer code tt2016 and receive 15% off your order!   Paul

Paul Olesen

Paul Olesen

 

The Four Stroke Dirt Bike Engine Building Handbook

I hope all of you have been getting out on your bikes and riding as much as possible now that spring is in full effect. For those of you in warmer climates, please don't remind me you have been riding year round without any additional layers, this only makes me jealous and forces me to seriously consider the thought of moving. I've been very busy the past month, but have tried to get a couple hours in on the bike every Saturday. There truly is no better therapy than going out and spanking the bike around after a long week of work! I'm very excited to announce that the eBook I have been working on these last four months, The Four Stroke Dirt Bike Engine Building Handbook, is officially released. I want to spend a little time talking about what the book has to offer you as a dirt bike engine building enthusiast; I don't think you will be disappointed. Below is a snapshot of the table of contents as well as a few interior pages, just to give you an overall look at what this book covers for you. What could this book possibly be about that other reference materials, like service manuals, don't already cover? I wrote The Four Stroke Dirt Bike Engine Building Handbook to be an all encompassing guide on engine building. Whether you are building a stock or performance engine, this book provides a specific framework for you to understand and use throughout the entire process. From the moment there is doubt about the engine's condition to the time the rebuilt engine is broken in, I give you a step-by-step guide to help you work towards a successful build. My aim was to create a definitive resource that hit on all the topics you may question as you proceed through an engine build, and teach you the how and why behind the way things are done. I've been very fortunate to work with talented engineers and builders over the years. This book is a way to share the knowledge I have learned from them with you, a way to bridge that gap for at-home engine builders to enable you to be better equipped with the proper insight and information when it comes time to rebuild. Today's modern four-stroke dirt bike engines are fine pieces of engineering, are designed to exacting tolerances, and require a great deal of care and precision in order to keep them operating at their finest. If you don't work with engines on a regular basis or haven't been taught by a great mentor, there are a lot of subtleties which can be overlooked that I've written extensively about for you. Throughout the book, engineering knowledge and practical experience are fused together to detail the how and why behind the way procedures are performed, parts are designed, and engine performance is affected. This is the most important and valuable aspect of the book, and it's something you won't find in any service manual. The book doesn't just tell you to bolt part A to part B, it teaches and explains the correct way assembly procedures should be performed and why it is necessary to do so. It also explains the intricate relationship between parts. For example, the interaction between the valve guides, seats, and valves must be understood in order to understand why valve seat cutting shouldn't be left to just anyone. Along with the practical building how and why, an entire chapter has been dedicated to detailing how performance parts affect engine performance. Within this chapter helpful suggestions are provided to aid you in choosing the correct components for your build, depending on your specific riding needs. If you don't work directly with engines on a regular basis, it is hard to acquire practical experience when it comes to diagnosing problems and detecting abnormally worn parts. Not knowing what to look for when inspecting engine components can lead to improper diagnosis and assembly of an engine, which could still have bad parts in it. I have filled the book with as many photos and written examples of worn or damaged parts as I could so that you will know exactly what to look for when inspecting engine components as you proceed through the build process. This is invaluable practical knowledge, which only comes with experience, and is not something you will find in your service manual. Now that you have a general feel for what the book is about you may have more questions. One I've been asked a few times now by friends and fans is how can you write a book applicable to all makes and models? Believe it or not, the variations of dirt bike engine designs between manufacturers are in truth very minimal. Sure, there are physical and locational differences. One brand may use two camshafts while another uses a single cam, or one may put an oil pump on the left side of the engine while the other puts it on the right, but the overall layout of the engines and function of the parts are all similar. I did not write this book with the focus being on the little differences between brand X and brand Y. I wrote this book outlining specific techniques and inspection points applicable to every type of engine you will encounter. The function and the way components interact does not change just because they are physically different or located in different places. This is imperative to understand in order to get the most out of the book. To ensure I've covered the various ways parts interact and can be assembled, I've used two different engines throughout the book as examples and have provided specific instruction on how to deal with assembly differences that will be encountered across the Japanese and European brands. If you have a thirst to learn more about how your engine works and a desire to correctly disassemble or assemble an engine to professional standards, you will benefit greatly from this book. Whether a complete beginner or a seasoned builder, with over 300 pages and 250 images worth of information, there is fresh and useful knowledge for everyone. There is also valuable material packed into this handbook that doesn't just pertain to the act of building the engine. I include instruction on diagnosing engine problems, sourcing and determining which parts to replace, using precision measuring tools, setting up your workshop, and additional tests and inspections that should be performed when preparing racing engines. If you just want to build your engine back up to stock spec, you are covered. If you want to go the extra mile and prepare a racing engine, you are also covered. In a way this book allows you to choose your own ending by giving you all the tools and knowledge you need to complete your build at whatever level you decide. The book is available in both print and eBook format. We ship worldwide and offer door to door tracking for overseas shipments. I also created a discount code just for the ThumperTalk community that gives you another 20% off the list price. Be sure to enter the code thumpertalk2015 before purchasing. Order the print book directly from our website or on Amazon. You can order the eBook directly from our website and it will immediately be sent to your email inbox. From there you can download it to your electronic device of choice to read or print. You also have the option to just view it online.  This is one tool you can add to your toolbox that won't wear out and break on you and can be used universally. Thank you for your support of DIY Moto Fix these last few months, and enjoy the heck out of the book! Thanks for reading guys and have a great week. -Paul Olesen DIY Moto Fix - Empowering And Educating Riders From Garage To Trail

Paul Olesen

Paul Olesen

 

The Top 6 Characteristics You Need To Have To Rebuild An Engine

I hope you’re all having a good fall and are getting excited for the holidays. It snowed for the first time this year here in Wisconsin and I’m getting eager for the lakes to freeze over so I can get out and ride the ice. I need to set aside a good 7 hours to stud my tires and set up my bike before that can happen though!   Today I want to talk about six characteristics that are necessary to have when one sets out to build an engine. I’ve detailed how to tackle many different jobs, but honestly that is only half the battle. If you’re in a rush or lack the desire to understand the reasons behind what you’re doing, you will make mistakes and miss out on important things. Listed below are the traits that I believe can help you take your build to the next level.   1. Being Detail Oriented
What’s worse than getting started on a build only to realize you didn’t buy an important replacement part? Focussing on the details of a project can feel tedious at times but can pay off in the grand scheme of things. Before I get started on a project I spend a hefty amount of time researching what parts I’m going to replace and where the best prices are. Also, I will have a solid idea of the sequences I’ll use for disassembly and assembly. Another good habit for the detail oriented is to take notes throughout the build, which you can use at a later date should the need arise. When you have an appreciation for all the small details that go into a build, it will make for a much smoother project.   2. Having Patience
Have you ever been in a rush to do something and after you’re done you realize if you had spent just a bit more time the project could have turned out much better? I was this way with so many of the things I did when I was younger, but have learned to slow down and be patient as I work. Engines don’t go together instantaneously and being patient throughout the process, especially when things aren’t going as planned, is very important. There is nothing worse than making a huge mistake because you’re in a rush. Imagine finishing a build and realizing you left an important part on the table, depending on where the part came from, you just bought yourself another few hours of work. Trying to skimp on time more often than not costs you more time in the long run. Have patience and enjoy the process.   3. Being Observant
Just about every mechanical thing is gleaming with a story, and that story only reveals itself if you know what to look for. An engine is no different. From the parting lines on a component left by the casting tooling used to create it to wear patterns on a piston, there are hundreds of observations that can be made while working on an engine. As you work, keep an eye out for subtle anomalies that may tell you why something failed or broke. For example, things like snail tracks across a gasket, raised edges on gasket surfaces, or covers that don’t sit flat on a table - these are all good indicators of why a particular part was leaking.   4. Being Curious
Perhaps more appropriately titled, “a desire to understand mechanical workings”. It is incredible how much can be learned about the engine just by studying how specific parts interact within it. An engine is composed of many different subsystems and they must all work in order for the engine to function. By looking at the various interactions of the parts within an engine, the condition of the parts and reasons for any failures can be more easily understood. The next time you build an engine, challenge yourself to learn how all the different subsystems of the engine work. Once you learn this, diagnosing problems and identifying all the faulty parts becomes much easier.   5. Being Meticulous
The necessity to be thorough and meticulous throughout a build cannot be overstated. Whether it be taking extra steps to inspect components, measuring new parts, or taking extra time to ensure the condition of surrounding subsystems are okay, having meticulous tendencies can pay off. As an example, on more than one occasion I’ve purchased new parts that have been mispackaged or out of spec. Had I not made the choice to carefully measure the problematic new parts, I could have ended up with an engine that was destined to fail. While it may take more time to be meticulous throughout a build, there is a lot at stake, both in terms of time and money, making it all the more important to ensure everything is done correctly.   6. Having Ambition
Building an engine can be hard, things can go south unexpectedly, and projects can easily stall. Being ambitious and having a can-do attitude is important to ensure the engine doesn’t sit half torn apart in the garage never to be completed. Until you tear into the engine, you never know what you might find. I’ve disassembled engines many times in the past only to find I need to replace a lot more parts than I had planned (this seems to be my luck when I shop for bikes on Craigslist as of late). This can be a huge downer, but keeping the end goal of getting back out and riding in mind and having the desire to push through any and all obstacles is a must.   Do you have any engine building characteristics you want to share? Leave a comment below and tell everyone what you think it takes to build a great engine!   For those of you that believe you possess the characteristics of a good engine builder, be sure to check out my book, The Four Stroke Dirt Bike Engine Building Handbook, to learn more about the how and why behind engine building. Whether you want to be taught about the relationships between all the various parts within an engine, you are in need of pointers on picking the right performance parts, or you would like to see examples of wear patterns found on engine components, my book is here to guide and help you throughout your build.   With the holidays coming up, I want to extend a special four day offer to you for the handbook and all the other products at DIY Moto Fix. Between November 27th and November 30th if you purchase anything from DIY Moto Fix you will save 30% on your order. If you’ve got a significant other trying to do some holiday shopping for you, be sure to send the site their way before Monday the 30th  
Save 30% and check out the book and other products by clicking this link: DIY Moto Fix

Paul Olesen

Paul Olesen

 

Premix Once - Measure Twice

Premix Once - Measure Twice I cringe when I see someone guess at the proper amount of oil to mix with their fuel when filling up their two-stroke dirt bike, snowmobile, jet-ski, or even weed whip. Manufacturer’s spend an awful lot of time figuring out what the right amount of oil is for a given engine application so when I see someone add a splash here and a splash there and call it good it worries me. If you’re one of those folks maybe after reading this it will worry you too. Adding too little oil may lead to improper lubrication of the crank bearings, rings, piston, and rod bearings causing premature failure due to excessive wear and increased friction. You might think using less oil will save you a few dollars, will lead to more horsepower, or will keep your spark plug from fouling. Let me assure you that buying another quart or gallon of oil is much cheaper than having to replace an entire top and/or bottom end. Personally I have not come across a single study that proved less oil lead to more horsepower. I have ran oil mixtures as rich as 20:1 and have not had any problems with the bike fouling plugs. In my opinion, plug fouling occurs from poor combustion (possibly caused by combustion chamber shape, spark strength, or ignition timing) not the amount of oil in the mixture itself. Let’s consider the effects of having an oil mixture that continually varies each time the bike is filled with fuel. As an example let’s say that the bike and carburetor is set up to run at a fuel/oil ratio of 40:1. What happens if we get generous with the amount of oil we add when we fill the bike up? Let’s say after we finish filling we end up with a fuel/oil mixture that is 20:1. Now the bike has much more oil in the fuel mixture than there was originally. There is no question that the engine will be well lubricated, but will the engine perform better or worse? Assuming that no changes are made to the carburetor to account for the richer oil mixture, the engine will most likely run worse. The reason being the amount of fuel able to pass through the orifice of the main jet, pilot jet, and needle circuit is reduced due to dilution caused by more oil. This will cause the bike to run lean and may lead to problems! While you may think you are doing the engine a favor by giving it more lubrication, unless the carburetor is adjusted to compensate for this change, you are actually increasing the chances of doing damage to the engine by running it lean. On the flip side we could decide to take our engine that is set up to run a 40:1 fuel/oil mixture and use less oil. Let’s say we are down to the last quart of oil and need to get a couple bikes through a weekend of riding so we skimp and run the bikes at 80:1. In this case the opposite will happen. Since there is less oil in the fuel/oil mixture, more fuel will be able to flow through our carburetor circuits, thus causing the bike to run rich. A rich bike is much better than a lean bike, but what if there is no longer enough oil to adequately lubricate the engine? If there isn’t enough oil to lubricate the moving components within the engine, it is highly likely that engine components will wear faster, run hotter, and ultimately fail. My advice to you would be to take the extra five minutes every time you mix to measure out the amount of gas and oil precisely. That way each time you fill the bike up you are giving your engine the most consistent fuel/oil mixture possible. Taking the time to do this will lead to more consistent performance, maintenance intervals, and save you a lot of money on an avoidable rebuild. If you don’t already have an oil measuring container go out and pick one up for a couple bucks and throw it in with your riding supplies so you are never in the situation where you have to guess. Another tip I want to share with you is when you are at the gas station filling up your container with premium, let the first gallon of fuel go to your car or truck. By doing this you purge the gas pump’s hose of whatever blend was previously dispensed and ensure you are in fact getting premium for your toys. Once done filling and mixing, I like to label my gas jugs with the date I mixed them and with the fuel/oil mixture I mixed. Doing these simple things will help avoid confusion down the road and a keep your engine healthy. Moto Mind - Empowering and Educating Riders from Garage to Trail If you'd like to follow my blog, click the "follow this blog" button in the upper right. I'd love to have you.

Paul Olesen

Paul Olesen

 

Motorcycle Ice Tire Studding - Part One

Happy belated New Year's! I hope the holidays were good to you and that you're looking forward to a new season of two wheeled excitement. I know I am and I'm excited to get back to work on this blog.   In today’s post I’m going to get into the details related to tire studding with the help of an industry expert. To help bring you the best information I can on studding ice tires, I’ve enlisted Jarrett King of Two Wheel Endeavors to help with this article. For those of you that don’t know, Two Wheel Endeavours is heavily involved in supporting Canadian ice racing efforts and offers studded tires, ice racing accessories, and custom ice solutions. Jarrett was involved in the development of the Mitas Ice King tires, knows his craft, and brings a lot of knowledge to the table.   Many people are under the impression that there isn’t much to studding a pair of tires, just screw some screws in and you’re done right? There is actually a hefty amount of skill involved with studding tires. These skills come down to knowledge of screw angle, head position, and screw length. Of course there are many parameters which all affect how well the tire will perform, but today we are going to talk mostly about studding. This attention to detail is a huge reason that guys who have perfected the art of tire studding can make a living at it. I’m not saying this to scare you off from trying to stud your own tires, just that if you’re going to go for it, it will take some practice and advice from an expert.   Now I’m going to turn it over to Jarrett who will go into detail on the aspects of tire studding.   Key Factors Affecting Tire Performance by Jarrett King   Tire Choice: Selecting the right tires to stud is critical in terms of traction and tire life. Lug height, tread pattern, carcass thickness, and rubber composition all have a huge influence on how well a tire will work. Unfortunately, there is not a lot of data supplied by tire manufacturers available to help guide a person in the right direction, but there is plenty of empirical data floating around among the ranks of ice riding enthusiasts. To help get you started I put together a list of the most common ice tire choices.   Front Tires
Mitas Ice King - (Top Left)
Bridgestone ED11 - (Bottom Right)   Rear Tires
Mitas Ice King - (Top Right)
Kenda K335 - (Bottom Left)
Motoz X-Circuit - (Not Shown)     Tire Liners: Depending on the tire chosen, a liner can be used that will provide protection for the tube and allows for the use of longer screws. The liner is usually a cut up street tire which fits inside the chosen tire.   Pattern: The pattern in which the screws are laid out on the tire has a huge influence on the traction and grip characteristics of the tire. Specific patterns may be tailored to provide more grip or slip depending on the rider and how the tire is used.       Consistency: Care must be taken to ensure the screw pattern is consistent from one lug to the next. Any deviation in screw location and angle can cause the tire to wander as it moves over the ice.     Rim Trueness: The trueness of the rim can have a big effect on how the tire performs. A wonky rim can cause inconsistency in screw alignment. This can lead to similar handling problems because the screw pattern is not aligned accurately.   Screw Type: AMA or Canadian style screws are the primary options for competitive ice racing. The two screw types are defined below:   AMA screws - 3/16” head height, sizes #8 or #10, and range in length from ⅜” to 1 ½”     Canadian screws - ¼” head height, size #12, and range in length from 1” to 1 ½”   Along with the screw requirements for the different racing classes, keep in mind purpose made ice screws go through a different hardening process than normal hardware store screws, allowing them to stay sharp longer. If you’re going to stud a pair of tires and want longevity, be sure to use a good quality screw such as those offered by Kold Kutter.   Screw Threads: Fine thread screws are preferred because they do less damage to the rubber during installation. They are also easier to set to the correct height when fine tuning the screws.   Screw Angle: The angle the screw is driven into the tire dictates how the screw contacts the ice. The screw angle can be broken down into two parts, the fore/aft angle, and the side angle. Sweep: Tire builders refer to the fore/aft angle of the screw as the sweep angle. Ideally only the leading edge of the screw should make contact with the ice. This can be achieved by angling the screw anywhere from 10 to 30 degrees upon installation.
Side Angle: Screws used to grip the ice when the bike is leaned over will be installed at an angle which complements the contour of the tire.

Head Alignment: The alignment of the slot in the screw head can be tuned to provide better grip in a given direction. For screws used for braking (front) and drive (rear) the screw slot is aligned perpendicular to the direction of travel. For cornering grip the slots of screws on the side of the tire are aligned parallel to the direction of travel.  
  Paul: Now that Jarrett has provided a great framework of what goes into studding a tire, we’re going to get into the specifics. It was mentioned previously that ice screws have three primary functions: braking, accelerating, and cornering. Next, we’ll get into the details of what makes each of these three types of screws functional for their specific purpose.   Braking Screws: Braking screws are at the rear of the lug on top, but when they are on the ground they are on the leading edge (biting edge) when under braking, thus the name “braking screw”. Sweep is used to prevent the screws from chattering on the ice under braking because of the fact that the crown would strike the ice at two points if installed flat. The magic sweep angle is the shallowest possible angle without the “rear” part of the screw crown biting in. With Canadian screws, this angle is much more straight up and down but still usually has 10 degrees or so. If you leaned them too far forward it will damage the knobs because the screw isn’t sunk into the liner enough, if you went straight in they will function but it makes the tire feel a bit strange under heavy braking.     Acceleration Screws: Again, there are differences between AMA and Canadian screws. The Canadian screws can go virtually straight in, AMAs need that biting edge so they don’t deflect or lose traction because of two different contact points. Picture a skate blade. The more sharp and precise the edge, the more ground pressure is focused on that area. Same with screw tips, if two parts of it hit the ice it will start to “float”. Optimal angle is shallowest possible (as close to straight up and down as possible) before the back edge of the screw starts touching the ice surface.
  Side Grip Screws: Cornering screws are typically run in at one angle, there is no sweep to them. Some builders have tried adding some sweep, however, never with too much angle. If you run an ice tire over a piece of cardboard under lean you will see that the top edge of the screw is contacting the ice at an angle that prevents the front tire from low-siding. In essence these screws do the exact reverse thing that the rear tire does under acceleration.     Paul: The last thing Jarrett is going to talk about is the screw pattern and some of the compromises that are made while studding.   Jarrett: When it comes to general screw pattern and arrangement, there are a couple things to consider. First, is that on the rear tire the inverse “V” pattern is there for a reason… what it does is each screw passes the load onto the next screw while under lean (picture them passing sandbags to each other). To prove this, reverse a V-pattern tire, it will be all kinds of squirrely under acceleration and then the rear will try to jump out from under the bike when you hit the brakes, it’s truly scary.   My second point, ideal screw pattern is a balance between a few different factors. Knob spacing, contact pressure and knob count/pattern. On a tire like a Kenda, so many screws are striking the ice at once that the tire is floating on the surface of the ice. Traction is being gained by getting the maximum number of screw heads to hit the ice at the same time. This is great until the moment that there is a hint of snow on the lake and the tire begins to act like a crazy carpet under the bike. It floats because it can’t maintain ground pressure.   The old Pirelli Lagunacross tire became amazing the moment that Marcel Fournier came out with the modern Canadian Ice screw. The knob pattern was ideal (V shaped paddle) for the application and the knob spacing was super wide, which meant great ground pressure on each screw. Unfortunately that also meant a much larger radial load on the screws and knobs which often lead to premature knob or screw failure. The Mitas Ice King does not generate the same ground pressure as the Pirelli because the knobs are quite a bit closer but the tire’s compound and knob pattern allow for a much better balance of ground pressure (traction) to durability ratio. Using AMA screws, a Mitas Ice King does not benefit from additional screw rows the way that a Kenda will because it will float much quicker, but without as many screws contacting the ice.   Ice tire building is a compromise. The perfect ice tire doesn’t exist in the same way that there is no perfect Intermediate MX tire… but there are some that are MUCH more effective than others.   My third and final point, ice tires have been built in north America since the early 30s. The angle of screws is something that has been tried in multiple arrangements hundreds of times over. For someone getting into the sport their enthusiasm may make them believe that changing things will create a magic setup, but the reality is that a true set of wheels (no dings dents, warps), with consistent screw angles and heights, proper air pressures, and properly balanced is the most effective way to kick ass out on the ice racing track. Oh and don’t forget to duct-tape that face (frostbite sucks!).   Paul: Whether you're new to the sport or have a few seasons under your belt I hope you found Jarrett’s info on ice tires beneficial . Check the DIY Moto Fix website for part two in a week and here again for part three. For those of you in warm states I encourage you to take a trip to a cold destination and give ice riding a try! Be sure to check out Two Wheel Endeavors if you're in need of tires or anything else ice racing related. If you have any comments or want to share some info please leave a comment below.   -Paul
DIYMotoFix.com

Paul Olesen

Paul Olesen

 

Precision Measuring For The At-Home Mechanic // Part 3

As we wrap up our final post on precision measuring for the at-home mechanic, I hope you have found this three part series on measuring helpful and informative. If you need a brush up or haven't gotten a chance to read Part 1 or Part 2, we compiled all three parts into a free guide for you. You can download your free copy by clicking here. This three part series comes right out of the book I published, The Four Stroke Dirt Bike Engine Building Handbook. I think you're going to love the in-depth knowledge and information provided in this book on four stroke dirt bike engine building. To learn more and order your copy click here. In this post I will be covering the final six precision measurement tools you have at your disposal. Each measurement tool in this post features a description of appropriate applications for the tool and a step-by-step tutorial on how to use it. This post is designed as a reference so that you can easily come back to it at any time as you become more comfortable using measurement tools during a rebuild. PLASTIGAUGE Plastigauge is one of the only measurement tools you won’t mind throwing away once you are done using it. Plastigauge is a measurement tool used to check the clearance between parts. The plastigauge consists of little strips of plastic which are inserted between two parts. Once assembled the plastic strip is compressed. The amount the strip compresses can be measured and correlated to a chart (supplied with the plastigauge) which defines the clearance for the measured compressed width of the strip. For engine building purposes plastigauge is ideal for checking clearances between engine components utilizing plain bearings. The plastigauge is a great tool for confirming clearance and measurements. Another plus is that unlike most other measuring tools, plastigauge is cheap! Plastigauge is usually sold in an assortment of sizes which cover multiple clearance ranges. Plastigauge strips will come in different diameters and each diameter will be capable of measuring a certain clearance range. Where to Use: Examples include cam to cam journal clearance, crank bearing to crankshaft journal clearance, and crank pin to rod bearing clearance. Calibrating Plastigauge Finally a measurement tool where no calibration is necessary. Just make sure you choose the appropriate size strip for your application. Also make sure the plastigauge is fairly new. Plastigauge does get old after awhile and using old plastigauge may not yield accurate results. Reading Plastigauge After the plastigauge has been compressed use a calipers to measure the width of the compressed strip. Record the width in your notebook. Then look at the clearance chart provided with the plastigauge to determine the clearance that corresponds to the measured width. Yes, it really is that simple. How To Use 1. Clean the parts being assembled 2. Insert a small strip of plastigauge between the parts being assembled. 3. Carefully lower the mating part down onto the plastigauge. Take great care to lower the part straight down so the plastigauge doesn’t move. 4. Install the fasteners used to secure the parts together. 5. Tighten the fasteners to the torque value recommended by the manufacturer. Follow any special tightening patterns that may apply 6. Carefully loosen the mated parts. Again, follow any special instructions for loosening provided by the manufacturer. 7. Remove the part. Check to see which part, if any, the plastigauge has stuck to. 8. Use a calipers to carefully measure the width of the plastigauge. 9. Refer to the chart provided with the plastigauge to determine the clearance which corresponds to the measured strip width. Tip: With a keen eye taper and out-of-roundness can also be spotted by using plastigauge. Keep an eye out for variations in strip width after it has been compressed for clues about the condition of the bore. DIAL INDICATOR A dial indicator measures variations in height by utilizing a plunger which travels up and down. As the plunger travels a dial gauge records the amount the plunger has moved. For engine building purposes a dial indicator is a handy tool to have when measuring valve lift and finding top dead center. There are a wide range of dial indicators on the market. Choosing the best one for engine building may be daunting if you’re not familiar with them. There are two main features you want to look for when selecting an indicator. The amount of travel the indicator has and the resolution of the indicator. Choose an indicator with around 1.0” (25mm) of travel which has a resolution of 0.001” (0.025mm). This type of indicator will work well for engine applications. In addition to the indicator getting a few accessories for the indicator will be beneficial. Most indicators are not sold with a base. Magnetic bases are really handy when setting the indicator up and provide a means of securing the indicator so it can’t move. Even when working with aluminum parts (ex. cylinder head) a magnetic base can be utilized by bolting a flat piece of steel to the aluminum part. Dial indicators usually come equipped with rounded contact points which are ideal for measuring flat surfaces. Occasionally you may encounter a setup which requires a different contact point. A variety of contact points are offered for indicators and having an assortment never hurts. Tip extensions are a must have if you plan on doing any deep depth work with the indicator. One situation which routinely requires a tip extension is when using the indicator to find top dead center of the piston. Tip extensions can be bought in multiple lengths. Where to use: Examples include measuring valve lift, and finding top dead center. Reading Dial Indicators Reading a dial indicator is very similar to reading a dial calipers. The only difference is the dial indicator’s gauge face is equipped with a second smaller dial face. For an indicator with a resolution of 0.001” the small face is divided into 10 graduations. Each graduation represents a tenth of an inch. The outer dial face is divided into thousandths of an inch. Each time the outer needle rotates one revolution around, the second small needle tallies a tenth of an inch. This eliminates the need for the user to keep track of how many times the needle has gone around. The total measurement is comprised of the number of tenths of an inch the smaller needle is indicating plus the number of thousandths the large needle is indicating. In the picture above the dial indicator reads _0.136". For metric and other resolutions of dial indicators the reading process is identical to the above. Take note of the units and resolution and proceed to read the indicator accordingly. Calibrating Dial Indicators Checking and adjusting the accuracy of dial indicators usually can’t be done easily in one’s own shop. For dial indicator calibration the indicator would have to be sent to a calibration lab. Fortunately, the applications an indicator is used for when building engines doesn’t require the utmost accuracy so calibration is seldom a problem. How To Use: 1. Clean the contact point of the indicator and the part which will be indicated. 2. Carefully set the indicator up so that it is fixed to a sturdy base which can’t move. 3. The amount of travel in each direction you will need depends on the specific application you are measuring. Consider the motion and travel of the part you want to measure and set the indicator accordingly so that it doesn’t run out of travel halfway through measuring. For example, when measuring valve lift you would want to engage the indicator so that around a quarter of the plungers travel has been used. 4. Square the spindle of the indicator being measured. The more square the indicator spindle is to the part the more accurate the readings will be. If the indicator is set at an angle to the direction of travel of the part the indicator will not read accurately. Keep this in mind and always try to set the indicator spindle as square as possible to the part being measured. 5. Zero the indicator by rotating the gauge face so the outer needle aligns with “0”. For example when measuring valve lift the zero point would be when the valve is fully closed. When checking runout the zero point may be a low or high point. 6. Move the part being indicated a few times returning it to its starting position each time. Check to make sure the indicator consistently reads “0”. If it doesn’t then carefully adjust the gauge face to realign the needle. 7. Once the indicator has been zeroed proceed to move the part being indicated and take measurements. 8. After measuring return the part to its original position. Occasionally an indicator can get bumped or something can happen during the procedure. This is a good way to confirm one last time that the indicator is still zeroed. DIAL TEST INDICATORS Dial test indicators are very similar to dial indicators, however their primary function is more as a comparative tool than a measurement tool. The main difference between a dial indicator and dial test indicator is the dial test indicator uses a contact point which pivots instead of a plunger that travels up and down. This pivoting action results in an arcing path instead of a straight up and down path. The test indicator is best suited for taking comparative measurements and zeroing runout. For engine building purposes this makes a pair of dial test indicators well suited for measuring the runout of a crankshaft. Just like dial indicators, test indicators are made with different lengths of travel and different resolutions. The most suitable resolution for crankshaft truing and inspection purposes is 0.0001” (0.0025mm). Most test indicators with a resolution of 0.0001” will have a travel of 0.008” (0.203mm) or 0.010” (0.254mm) which will be suitable for crankshaft inspection. The test indicators will require fixturing so having a pair of bases, stands, and clamps is necessary. Fortunately, the test indicators use similar mounting systems as dial indicators so if you have fixturing for dial indicators you are all set to mount the test indicators. Where to use: Examples include crankshaft inspecting or truing. Reading Dial Test Indicators The gauge face of a dial test indicator is symmetrical. The face is divided into graduations based on the resolution of the test indicator. Each side of the face represents half of the total travel of the test indicator. Reading the gauge is simply a matter of determining how many graduations the needle has moved from its starting point to its ending point. Calibrating Dial Test Indicators Like dial indicators, calibrating dial test indicators is usually done by a professional calibration lab. As long as the test indicator is well cared for the need for calibration should be infrequent. How To Use: Since the contact point of the test indicator travels in an arc the way the indicator is set up has an impact on measurement. This is the main reason test indicators can’t be relied on heavily for taking measurements and instead are used for comparing. 1. Clean the contact point of the indicator and the part which will be indicated. 2. Carefully set the indicator up so that it is fixed to a sturdy base which cannot move. 3. Most test indicators function best when the contact point is perpendicular to the direction of travel of the work piece. Some indicators differ slightly and should be set at a slight angle, so confirm with the instructions supplied with your test indicator to attain the correct orientation. 4. The majority of test indicators work best when the contact point is preloaded. As a rule of thumb a 1/10 - ¼ revolution of the needle is about right for setting preload. Instructions supplied with individual indicators may have specific preload instructions. 4. Rotate the part to find the high or low point. Zero the indicator by rotating the dial face so the needle aligns with “0”. 5. Move the part being indicated a few times returning it to its starting position each time. Check to make sure the indicator consistently reads “0”. If it doesn’t then carefully adjust the gauge face to realign the needle. 6. Once the indicator has been zeroed proceed to move the part being indicated and take measurements. 7. After measuring return the part to its original position. Occasionally an indicator can get bumped or something can happen during the procedure and this is a good way to confirm one last time that the indicator is still zeroed. TRANSFER GAUGES Transfer gauges are measurement tools which don’t yield a direct measurement. They are simply tools which can be used to transfer the dimensions of something requiring measurement to a measurement tool. There are two types of transfer measurement tools commonly used in engine building, small hole gauges and telescoping gauges. Transfer gauges can be tricky to use accurately for a couple reasons. First, they introduce a second source for error. Instead of taking a direct measurement the measured part must first be sized using a transfer gauge. Then the gauge must be measured by a measurement tool such as a micrometer. It is easy to see how mistakes can accrue in this situation. Second, transfer gauges rely heavily on feel to obtain accurate measurements. If the user of the gauge is unskilled, the transfer measurements could be all over the board. Taking these points into consideration transfer gauges can still be incredibly helpful when measuring engine parts. Transfer gauges are one of the most relied on methods of accurately measuring internal diameters. SMALL HOLE GAUGES Small hole gauges are used to transfer internal measurements usually less than ½” in diameter. A small hole gauge has a split in its head which allows the head to expand or contract to the size of the part being measured. An adjustment knob at the end of the handle is turned to expand or contract the head. The head on the gauge can either be a full or half sphere design. The half sphere designs have the advantage of being able to measure blind holes. Small hole gauges are usually sold in sets capable of measuring from around 0.125 - 0.500” (3.175 - 12.4mm). Each set is comprised of around four gauges with each gauge being able to measure a certain portion of the set’s total range. For engine building purposes, small hole gauges are primarily used to measure the inner diameters of valve guides. Where to use: Valve guides How to use: 1. Clean the bore of the part to be measured and the head of the small hole gauge. 2. Slowly turn the adjustment knob on the gauge expanding the head of the gauge inside the bore of the part being measured. 3. Simultaneously, gently rock the gauge back and forth and fore and aft inside the bore until the head of the gauge just starts to drag on the bore of the part. As you rock back and forth make sure the handle of the gauge passes through the point where the handle is square to the bore. 4. Remove the gauge. 5.Use a micrometer to measure the diameter of the gauge to determine the diameter of the part’s bore. Since the gauge can easily be compressed little to no pressure can be applied by the measuring faces of the micrometer. 6. Slide the gauge back and forth and fore and aft as you delicately tighten the ratchet or thimble of the micrometer. An accurate reading will be obtained when the micrometer just starts to drag against the gauge. Remember to measure perpendicular to the split in the gauge. 7. Lock the the spindle of the micrometer and read the micrometer to obtain the bore diameter. Hot Tip: Since this is partly an exercise of feel, take multiple measurements until the measurements start to yield the same results. This way you can be certain the measurements are accurate. TELESCOPING GAUGES Telescoping gauges are the big brothers of the small hole bore gauges. Telescoping gauges are shaped like a “T”. A tightening knob is situated at the handle end and it controls one or two spring loaded plungers (dependent on gauge type). Once the knob is loosened the plunger(s) expand outwards to capture the diameter of the bore being measured. The plunger ends are convex so the gauge can be rocked back forth to obtain the measurement. Telescoping gauges are usually sold in sets capable of measuring from around 0.3125 - 6.0” (8 - 152.4mm). Each set is comprised of around six gauges with each gauge being able to measure a certain portion of the set’s total range. Where to use: Examples include lifter bucket bore and cylinder bore. How to use: 1. Clean the bore of the part to be measured and the ends of the plungers on the telescoping gauge. 2. Set the gauge inside the bore with one plunger touching the side of the bore. 3. Slowly loosen the adjustment knob on the gauge handle expanding the plungers of the gauge inside the bore of the part being measured. http://www.thumpertalk.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=231329 4. Set the gauge up so that the handle is just out of square with the bore. 5. Tighten the adjustment knob down. 6. Gently wiggle the gauge back and forth while passing the gauge through the bore. Only pass the gauge through the bore once. This will center the gauge and set the plungers to the diameter of the bore. http://www.thumpertalk.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=231330 7. Clean both measuring faces. 8. Use a micrometer to measure the diameter of the gauge to determine the diameter of the part’s bore. Since the gauge can be compressed, little to no pressure can be applied by the measuring faces of the micrometer. 9. Slide the gauge back and forth and fore and aft as you delicately tighten the ratchet or thimble of the micrometer. An accurate reading will be obtained when the micrometer just starts to drag against the gauge. [series of pics showing measurement direction 10. Lock the the spindle of the micrometer and read the micrometer to obtain the bore diameter. Hot Tip: Since this is partly an exercise of feel, take multiple measurements until the measurements start to yield the same results. This way you can be certain the measurements are accurate. V-BLOCKS A V-block is a large precision machined metal block with a V in it. During an engine build V-blocks are used primarily for checking runout of cylindrical parts such as the crankshaft. http://www.thumpertalk.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=231331 When shopping for V-blocks a precision ground matched set should be purchased. Fancy versions may come with magnetic bases, multiple Vs, clamps, or rollers. While some of these features are nice they certainly aren’t necessary and add to the cost. That wraps up our three part series on precision measuring for the at-home mechanic, thanks so much for reading! If you would like all this precision measuring information in one place so you can come back and easily reference it, we created a free guide for the ThumperTalk community that you can download right to your computer or phone. Click here and I'll email the The At-Home Mechanic's Guide To Precision Measurement right to you so you can have it organized in one place. If you are interested in owning a copy of The Four Stroke Dirt Bike Engine Handbook, you can learn more by clicking here. Thanks again for reading and feel free to leave a comment below! -Paul Olesen DIY Moto Fix | Empowering And Educating Riders From Garage To Trail.

Paul Olesen

Paul Olesen

 

How To Repair Your Clutch Basket Dampers For Less Than $30

How to repair your clutch basket dampers for less than $30? Most modern clutches incorporate rubber dampers which help reduce torque fluctuations through an engine’s drivetrain. Single cylinder engines (four-strokes especially) have high peak torque fluctuations since they only fire once every fourth stroke. The dampers situated between the clutch driven gear and clutch basket help smooth out the delivery of power to the gearbox and rear wheel.   The rubber dampers wear out from normal use and in most cases can be replaced. Replacement of the dampers is a fraction of the cost of buying a new clutch basket, does not require a lot of special tools, and you aren’t out anything if the project doesn’t go as planned.   Before I get into the details of replacing the dampers, you are probably wondering how you can tell the dampers are worn out. When the engine is running some additional gear noise coming from the clutch may be noted, but honestly this is a problem difficult to diagnose when the engine is together. Finding this problem is much more likely when servicing the clutch pack or performing other work on the engine.   The easiest way to determine if the dampers have worn is by trying to rotate the clutch gear independently from the clutch basket. Depending on how worn the dampers are this may take a little bit of force, so it is best to lock out the clutch gear and primary drive gear. Once locked, the basket can be rotated back and forth to check for free play. Alternatively the clutch gear can be clamped in the soft jaws of a vice while trying to rotate the basket back and forth. The clutch basket should not move independently from the clutch gear.   In the first photo note the alignment marks are perfectly aligned. In the second photo the marks have shifted about an ⅛” (3mm). This may not look like much, but it will feel like a lot when you twist the basket.     In order to replace the worn dampers the clutch gear will have to be removed from the clutch basket. Rivets are used to secure the gear to the basket and the rivets will have to be drilled out in order to remove the backing plate, gear, and dampers. Once the rivets have been removed, the old holes can be tapped and bolts installed to secure the gear to the basket.   Prior to starting this project you’ll want to make sure you can source new dampers for the clutch basket. Aftermarket clutch manufacturers often offer replacement dampers for their clutches which can work equally well in a stock basket. Hinson, Wiseco, and others supply “cushion kits” which can be purchased from their respective websites, through Ebay, Amazon, or anywhere else you may like to do your motorsport shopping.   Before attempting to dismantle the clutch basket, check to see how much clearance is between the rivets and other features on the engine. Usually the idler gear will be the closest in proximity to the rivets. If the engine has an oil pump gear driven off the clutch, the oil pump gear may also be close to the rivets. Make a mental note of the clearance for future reference. The clearance between the parts when using bolts should be roughly equal to the clearance between the parts when the original rivets were used.     How successful you are at removing the old rivets will in large part dictate the size of the new bolts required. I made a couple of mistakes when repairing my clutch basket, so I ended up using bolts larger in size than I intended. The first mistake I made was a very silly one in hindsight. I didn’t realize that on this particular clutch the rivets are countersunk. Anytime countersunk rivets are used, grinding their heads off won’t work.     Instead of grinding, the rivets should be drilled from the back side. Use a center punch to help get the drill bit started on the right track.     Start with a small bit to create a pilot hole. Once the pilot has been created estimate the diameter of the rivets and select the corresponding bit size.     The diameter of the rivet can be deceptive since both ends have been mushroomed. Most rivets will either be 5 or 6mm in diameter. Err on the safe side and start with a 5mm (#9 bit) before moving up in size. This way if everything is done correctly a 6mm x 1.00 tap can be used to thread the holes. I made the mistake of thinking I was dealing with 6mm rivets so I drilled my holes larger than necessary leaving me with no option but to use an 8mm x 1.25 tap and large 8mm bolts.     Once all the rivets have been drilled, the backing plate can be removed and the rubber dampers will expose themselves. At this point it should be easy to see how the dampers have deformed and no longer fill in the holes properly. The dampers can be directional so take note of the orientation of the dampers at this time.     The dampers may also show signs of cracking and other damage.     Next, you’ll want to determine what bolts to use to secure the gear and backing plate back onto the clutch when it comes time to reassemble the clutch basket. Bolt size will strictly depend on the hole size you drilled to in order to remove the rivets. Ideally, the bolts will only be slightly larger than the original rivet, as this will allow for the easiest clearance between the bolt head and the idler gear. Keep in mind the following tap drill sizes for common metric bolt diameters and thread pitches.   6.00mm x 1.00 - #8 drill bit   7.00mm x 1.00 - letter “B” or 15/64” drill bit   8.00mm x 1.25 - letter “H” or 17/64” drill bit   The bolt head type will come down to your given clearance requirements between the backing plate and idler gear. You may find that a countersunk or button style head will work well. A great resource for selecting fasteners is at McMaster-Carr. If you’ve never explored McMaster-Carr you’ll quickly come to find that they sell just about everything under the sun and if you’re not careful you may part with more money than you originally intended! A few other good sources for metric hardware include Ebay (simply type in the bolt type you’re searching for in the search to turn up lots of results), Maryland Metric, and Boltnet.   For my basket I chose an 8mm x 1.25 Grade 12.9 socket head button which was 14mm long. Once the bolt has been selected, the backing plate and basket can be modified to suit. Start by enlarging the backing plate so that it will accept the bolts.     Once the backing plate has been drilled, if necessary, drill the basket rivet holes to the correct size so that the holes can be tapped. Be very careful when centering the drill bit in the hole. The more precise you are in this step the better the backing plate holes will align. Since the bit may have wandered a little bit when drilling the rivets out, it may be impossible to get everything centered just right. This isn’t the end of the world and adjustments can be made to the backing plate to get it to fit correctly.     Once all the holes have been drilled, carefully tap them using an appropriately sized tap.     After all the holes have been tapped, carefully add a chamfer to the top of the hole. This will deburr the hole and remove any raised edges which may keep the backing plate from sitting flat against the bosses. A drill bit larger in diameter than the hole or a deburring tool can be used to deburr the edge of the hole.     Proceed to fit the backing plate to see how the holes are lining up. As you can see, my holes wandered quite a bit when I drilled them so my backing plate holes don’t align well with the basket holes. I’ve shaded in with blue marker where I need to elongate the hole in order for the bolt to fit. Make sure an alignment mark is added to the backing plate and basket since the hole pattern is no longer symmetrical.     I used a rotary burr to elongate the holes, however, a hand file will work just as well. It will require a little more elbow grease and take a little longer though. Deburr the backing plate to remove any burrs which may keep it from sitting flat against the clutch basket bosses.
After making adjustments to the holes, all the bolts should easily thread into their respective holes.     At this point the clearance between the bolt heads and gears can be checked. As you can see, my bolt heads are too tall and will need to be ground down once they are permanently installed.     Grinding the heads is not ideal, but it ended up being inevitable for my application. Any necessary grinding will take place after final assembly since there may not be enough engagement between the bolt and bit.   After clearances have been checked and everything is ready for final assembly, the parts should all be thoroughly cleaned to remove any metal debris stuck to them. The clutch gear and new dampers can be reinstalled. If the dampers are directional, make sure they are installed in the correct orientation.     Next, install the backing plate. Apply a permanent thread locking agent to the bolts. Then install all the bolts. The diameter of the bolt and grade will dictate how it should be torqued. For your reference with the locking agent applied, I torqued my Grade 12.9 8mm x 1.25 bolts to 30Nm. Follow this link to view guidelines for torque specs on other metric fasteners.     If you were successful in selecting a bolt that clears the gears behind the clutch then you can give yourself a pat on the back as your work is done! If you are using bolts which must have their heads shortened this can be done using a grinding disc, mill, or any other suitable tool. Remove material from the bolt heads slowly and take just enough away so that the head clears the idler gear and any other obstacles.     I ended up removing most of the head and won’t be able to tighten or loosen the bolts, however, I planned for this prior to grinding. Removing the bolts isn’t a great concern because other parts of the basket such as the fingers will wear out sooner than the dampers will.     In total this fix cost me just under $30 and will prolong the life of my clutch basket. With this write up you should also be able to repair clutch baskets with worn dampers, save yourself money, and prolong the life of expensive engine parts.   If you have questions, thoughts, or want to share your experiences - leave a comment below!   Thanks for reading guys and have a great rest of your week.   -Paul Olesen
DIY Moto Fix - Empowering And Educating Riders From Garage To Trail

Paul Olesen

Paul Olesen

 

Precision Measuring For The At-Home Mechanic // Part 1

This week I want to provide you with some in-depth knowledge on the world of precision measurement. As at-home mechanics who want to take their rebuilding skills to the next level, learning about precision measurement and how to properly use precision tools is the final frontier. This post comes right out of The Four Stroke Dirt Bike Engine Building Handbook, the engine building book I am currently writing for my fellow riders who want to bring their engine building skills into a professional realm in their own garage. This post is part one of three that will cover the correct use and implementation of precision measurement tools when rebuilding your own engine. The world of measuring is so complex by nature that one could get wrapped up writing an entire book on the subject and still not cover it all. This is not my intention with my engine rebuilding book. My aim is to provide you with the principles on how measuring works, what the most important takeaways are on the subject of measuring, and an overview of how to use the tools correctly. Once informed you can then delve further into the intricacies of measuring for your own needs. There are three terms that are important to the fundamental understanding of measurement. These terms are often mixed up, confused as meaning the same things, or used incorrectly. These terms are accuracy, precision, and resolution. Understanding these three terms will go a long way in ultimately understanding measuring and the capabilities of measurement tools. ACCURACY Accuracy is how close a given measurement is to the “true” value of an object. For example, if a valve stem was exactly 0.1969” (5.000mm), accuracy would quantify how close the measurement tool was to the true value. PRECISION Precision is a measurement of repeatability. For example if an object was measured five times, precision would quantify how close the five measurements are to one another. Another way to think of precision is the finiteness of which a measurement tool can be read repeatedly and reliably. RESOLUTION Resolution is the smallest distinguishable value of a measurement tool. If a ruler is divided up into tenths of an inch then the resolution of the ruler is one tenth of an inch. A micrometer that can be read to one ten thousandth has a resolution of one ten thousandth of an inch. Just because a measurement tool, such as a micrometer, has a very fine resolution doesn’t mean it will be accurate or precise to that resolution. This will be explained more shortly. Distinguishing the difference between accuracy and precision is most easily done with a set of pictures. Four scenarios can occur when measuring. A measurement can be both accurate and precise.
A measurement can be accurate but not precise.
A measurement can be precise but not accurate.
A measurement can be neither accurate nor precise.
It is imperative when measuring engine parts that the measurements are both accurate and precise as represented in the first picture. Precise and Accurate Accurate but not Precise Precise but not Accurate Neither Precise nor Accurate Now let's see what happens when the bullseye is taken out of the picture: Notice that if the bullseye is taken out of the picture there would be no way to reference if the shots were accurate? It would be easy to tell that the “accurate but not precise” and “neither precise nor accurate” scenarios didn’t yield meaningful results. However, the scenario with “precise but not accurate” results could be misleading for someone measuring. This is exactly why it is important to calibrate measurement tools before using them. By calibrating a measurement tool you ensure it is accurate prior to measuring an unknown object. What Affects Accuracy and Precision? Now that the key parts of accuracy, precision, and resolution have been outlined how do they apply to measuring tools and measuring? I want to go over three factors that lead to variation in accuracy and precision when working with measurement tools. 1. Type of Tool and Tool Quality Different types of measurement tools will have different ranges of accuracy. For example a digital 0-6” calipers is usually accurate to 0.001” (0.025mm), however it will have a resolution of 0.0005” (0.0127mm). Just because the resolution is 0.0005” (0.0127mm) doesn’t mean that is how accurate the tool is. For a 0-1” micrometer the accuracy is 0.0001” (0.0025mm) and so is the resolution. Be sure to keep accuracy and resolution in mind when using and shopping for measurement tools. Decent measurement tools should have the manufacturer’s accuracy specified in the tool description. Using a calipers to measure the bore of a cylinder is a good example of using a measurement tool which is not accurate enough for the task at hand. Most dirt bike cylinder bores have a diametric range in the neighborhood of 0.0006” (0.0152mm), taper limit of around 0.0004” (0.0102mm), and out of round limit of around 0.0004” (0.0102mm). A calipers is off an order of magnitude in accuracy and is not capable of doing the job. 2. Temperature The temperature a measurement is taken at can have a large effect. A standard has been set for the temperature parts are measured and inspected to in the engineering and metrology worlds. That standard temperature is 68°F (20°C), which is what you should strive for when you are precision measuring parts. The reason temperature is important is due to the concept of thermal expansion. In a nutshell thermal expansion explains how an object’s volume will change as temperature changes. As volume changes so does length, which is what matters in this case. Equations for linear expansion will be used to show the role temperature plays on the diameter of a cylinder bore at two extremes: 32°F (0°C) and 100°F (37.78°C). Consider a cylinder that has a bore of 3.7795” (96.000mm) - typical of a 450cc engine. At 68°F we will say the cylinder measures exactly 3.7795” (96.000mm). What happens when the same cylinder is measured at 32°F (0°C) and at 100°F (37.78°C)? Let’s work it out. The formula for linear expansion is: ∆L = α x D x ∆T where: ∆L = Change in diameter of the cylinder bore α = coefficient of thermal expansion for aluminum (13.3 x 10^-6) in/in °F D = original diameter of the cylinder ∆T = Change in temperature (Final Temperature - Initial Temperature) α = (13.3 x 10^-6) in/in °F D = 3.7795” ∆T = 32°F - 68°F = -36°F Now it all gets put into the equation and solved. ∆L = (13.3 x 10^-6) in/in °F x 3.7795” x -36°F = -0.0018” ∆L = -0.0018” (0.046mm) So the 3.7795 inch cylinder has now shrunk to 3.7777 inches (95.954mm). A 36°F (20°C) change in temperature has caused the aluminum cylinder bore to change by 0.0018” (0.046mm)! In terms of cylinder measurements this is a big change and illustrates just how important it is to measure engine components in the right environment. A similar change can be seen when the cylinder is measured at 100°F (37.78°C). α = (13.3 x 10^-6) in/in °F D = 3.7795” ∆T = 100°F - 68°F = 32°F Now it all gets put into the equation and solved. ∆L = (13.3 x 10^-6) in/in °F x 3.7795” x 32°F = 0.0016” ∆L = 0.0016” (0.041mm) So the 3.7795 inch cylinder has now grown to 3.7811 inches (96.041mm) . In conclusion if you work in environments that are at one extreme or another on the temperature spectrum you are guaranteed inaccurate measurements. The scenario where measurements are precise but not accurate would be a good illustration for how temperature affects measuring. 3. User Error Lastly, the person doing the measuring also has an effect on the precision of the measurement. Another example is the most effective way to illustrate my point. Consider a situation where an inexperienced measurer measures a part five times and returns five different measurements. Next, a seasoned measurer measures the same part five times and returns the exact same measurement all five times. Both people measuring used the same measurement tool and carried out the measurements at the same temperature. The only variable that wasn’t the same was the person doing the measuring. This variation of measurement between people measuring isn’t that uncommon and happens all the time. Even two different seasoned professionals who inspect and measure parts daily can end up with different measurements for the same part. It is very likely that the variations in the professionals’ measurements will be much more precise when compared to one another. How do I know my Measurements are Accurate and Precise? Alright we’re starting to get into the more interesting - I mean practical, aspects of measuring. Hopefully the last few sections haven’t bored you or deterred you from wanting to measure your own engine components. I assure you, with practice and patience you can become a well versed measuring machine! I want to touch on some practical ways to determine if measurement tools are working correctly. If you went out and bought a cheap or expensive set of micrometers with measurement capabilities ranging from 0-6” how would you know they are accurate right out of the box? Is the manufacturer responsible for insuring they are accurate? Do they ever lose accuracy? Does the fact they were either cheap or expensive matter? The answer to all these questions is that prior to use, regardless of price or quality, most measurement tools will require calibration. Calibration is the practice of checking or setting the accuracy of a measurement tool to a known value. For measurement tools such as calipers and 0-1” micrometers simply ensuring the tips of the tool are clean, closing them together, and making sure the tool reads zero may be all that is necessary. This is a fairly easy method of calibration for these two tools, but isn’t possible for measurement tools where the tips don’t close together all the way (ex. 2-3” micrometer) or the tool has tips that extend outwards (ex. dial bore gauge). For these situations measurement gages are necessary for accurate calibration. Calibration gages (sometimes called standards) come in several varieties depending on tool application. The most common and applicable to engine inspection are gage blocks and ring setting gages. Gage blocks are small blocks of steel (more expensive variants come in other materials) which have been finished to extremely tight tolerances. Gage blocks are toleranced into several different classes. For engine inspection the most accurate measurements that must be made are to 0.0001”(0.025mm). In the measuring world the rule of thumb for calibrating tools is to use a standard which is at the minimum four times as accurate as the tool. So for a micrometer which is accurate to 0.0001” a gage block with an accuracy of at least +/- 0.000025” should be used. What the measuring world does and what the at home engine builder can do feasibly are two different things. For the majority of us our measuring abilities will get in the way of our accuracy long before the gage block used to calibrate the tool has any effect. For this reason I would suggest that using the standards which come with the tools will be fine and not splitting hairs over not knowing the exact accuracy of the standards. If you are shopping for a 0-6” set of micrometers most decent sets will come with standards blocks. The standards will usually come in 1, 2, 3, 4, and 5 inch sizes so all the micrometers can be calibrated at any time. Ring setting gages are similar to gage blocks and are also used for calibrating measurement tools. They are, as the name suggests, rings that have been machined to very fine tolerances. Usually instead of having a tolerance range that the ring falls into the ring will be stamped with the exact diameter it was machined to. A measurement tool such as a dial bore gauge is then calibrated to the exact diameter of the ring setting gauge. Ring setting gages are generally quite expensive as they are challenging to make accurately. Okay, I Understand the Importance of Calibrating My Measurement Tools. What About Making Precise and Repeatable Measurements? Precision gets complicated pretty quick because you have to factor in the measurement tool, temperature, and user taking the measurements. These three variables are difficult to separate completely. However, out of the three variables the user is usually the most likely variable to have a large influence on the precision of the measurement tool. In order to make precise and repeatable measurements it is important to do as many things the same as possible. Here are some things I recommend doing to make sure your measurements are as precise as possible. 1. Make sure the temperature in the room you are measuring is at 68°F (20°C). 2. Try to perform measurements of a part or set of mating parts in a short time period. There’s no need to rush the measurements or to measure all the parts in one day. It’s not that critical but, for example don’t measure the diameter of the piston one day and then wait to measure the bore of the cylinder. That doesn’t make sense. 3. When using micrometers use a micrometer stand to secure the micrometer in place. Not only will this make positioning the part easier and the micrometer easier to read it will also keep the heat of your hands from warming the micrometer. Remember thermal expansion? Believe it or not there are actually studies out there detailing how body heat makes a micrometer expand in length. It’s a minuscule amount but nonetheless worth mentioning. 4. A lot of measurement tools are operated by feel. When working with these tools try to be as consistent as possible when turning the handles. The amount of pressure you apply can have a big effect on the final measurement. For example, the difference between a part that drags hard through the tips of the tool versus one that drags but is soft in feel could be several ten thousandths of an inch. 5. Use your fingertips and a light grip. The fingertips are one of the most sensitive parts of the human body. As such they can be utilized to feel subtle variations in measurement. 6. Instead of just taking one measurement take 3-5. This is something you should definitely do when calibrating your measurement tools. By taking multiple measurements you’ll quickly get a feel for how precise your measuring is. If you are all over the board there is a good chance your technique is inconsistent. If you are within a ten thousandth or two each time you are on to something. For important measurements like cylinder bore diameter, taper, and out of roundness take 3-5 measurements. Then take the average of these measurements and use the average as your final measurement. 7. If you are struggling to determine if your measurement tools are working properly compare them to another known good set. If the two sets are not reading close to identical there is probably a problem with the unknown set. 8. Compare your results to those of someone with a lot of measuring experience. If a seasoned machinist can get your measurement tool to repeat to a ten thousandth of an inch it is probably not the tool. If you have the opportunity to get help from a machinist or someone fluent with measuring watch them carefully. Ask them questions, study how they work the tools, and learn from them. 9. Be patient and take your time. Rushing the measurement process is not a good idea and can lead to silly mistakes. You need to be in a state of mind where you don’t feel rushed and don’t mind taking the time to do a thorough job. 10. Write your results down! Write down everything clearly from the calibration measurements, any calculated averages, and measurements of specific parts. By writing things down you can easily work backwards to see if a mistake has been made somewhere. By keeping in mind accuracy, precision, and resolution you are well on your way to precision measuring like a pro. As I stated earlier, this takes a hefty amount of practice and patience. In my next post Precision Measuring For The At-Home Mechanic // Part Two, I will be discussing in complete detail how to properly use specific measuring tools. There is a definite finesse to using each of these tools as you rebuild your engine, and as you just learned in this post there are many factors that contribute to a precise measurement. Part Two will be posted to the DIY Moto Fix Website next week and you can have it sent right to your email inbox by subscribing to my eNewsletter by clicking below. Subscribe To The Moto Fix eNewsletter Thanks for reading and happy wrenching! -Paul Olesen Moto Mind - Empowering and Educating Riders from Garage to Trail www.DIYMotoFix.com

Paul Olesen

Paul Olesen

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