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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 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

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


Checking and Setting Cam Timing

Today I'm going to cover how to check and set cam timing, which is something you can do if you have adjustable cam gears in your engine. This is a procedure often performed by race engine builders to ensure the valvetrain performs just as they intend, and ultimately so that they extract the desired performance out of the engine. Adjustable cam gears typically aren't a stock option but are abundantly available in the aftermarket. The following text is exerted from my book, The Four Stroke Dirt Bike Engine Building Handbook, so if you find this info valuable please take a look at the entire book.  

Degreeing the camshafts is the process of checking, and if necessary altering, the cam timing so that the timing is set perfectly to specified timing values. On stock and performance engines, cam timing can be off slightly due to manufacturing variations in parts such as the camshafts, cam gears, cam chain, cylinder, cylinder head, crankshaft, crankcase, and gaskets. With so many parts having an influence on cam timing, it is necessary to adjust and correct the timing so it coincides precisely with the desired timing values.  The biggest factor determining how the camshafts must be timed is whether the cam lobes are symmetrical or asymmetrical. Camshaft lobes that are symmetrical have opening and closing ramps that share the same profile. Asymmetrical cam lobes have opening and closing ramps with different profiles. Symmetric and asymmetric camshafts are timed differently. First we will focus on the timing of symmetrical camshafts. Symmetric camshafts are timed most accurately by determining the position of the camshaft’s lobe center in relation to crankshaft position. A camshaft’s lobe center is where peak lift occurs, which is the most important timing event of the camshaft. Since the tip of the camshaft is rounded, it would be difficult to determine the lobe center by taking a direct measurement of peak valve lift. The opening and closing points of the camshaft are also of little use because the cam opens and closes gradually. This makes it difficult to determine the precise position in which the camshaft opens or closes the valves.

The lobe center position is a calculated value based on the position of the camshaft at two specific points of valve lift, typically with valve clearances set to zero. Normally the position of the camshaft is recorded at 0.050” (1.27mm) of lift as the valve opens and 0.050” (1.27mm) of lift when the valve closes. By recording the position of the camshaft at a specific valve lifts, the cam lobe is on a predictable portion of the opening and closing ramps. The center of the cam lobe is exactly in the middle of these two measurements. To calculate the lobe center of a symmetrical cam lobe you will need to do the following: 
1. Add the measured opening and closing timings together
2. Add 180 degrees to the sum
3. Divide the answer by 2
4. Subtract the smaller value of the two opening and closing numbers from the answer to reach the lobe center value.

Once the actual lobe center value has been determined on the engine, it can be compared to the specified lobe center timing presented by the manufacturer, aftermarket cam supplier, or the engine tuner. If the measured lobe center position coincides with the targeted position, all the work is done. If not, the cam gear will need to be adjusted so the timing is corrected. 

If you are checking the timing on stock cams and lobe center information isn't presented, you will need to determine the lobe centers the manufacturer recommends. To do this, the opening and closing timing information supplied in the service manual can be used. Aftermarket camshafts should come with a timing card full of useful information to set the cams correctly if they are adjustable, otherwise the lobe centerline can be calculated if the opening and closing timings are known. If you don’t like math, there are plenty of lobe center calculators available on the internet you can use. 

For the Kawasaki KX250F engine with the stock camshafts, the timing information is as follows: 

Intake Opens 40° BTDC (Before Top Dead Center)
Intake Closes 72° ATDC (After Top Dead Center) 
Intake Lobe Center = ((40 + 72 + 180) ÷ 2) - 40 = 106° 

My calculated lobe center timing is 106°. When I check the cam timing, this will be the value the real engine hopefully yields. The lobe center for the exhaust cam can be found the same way. For the KX250F exhaust cam: 

Exhaust Opens 69° BBDC (Before Bottom Dead Center)
Exhaust Closes 49° ATDC (After Top Dead Center) 
Exhaust Lobe Center = ((69 + 49 + 180) ÷ 2) - 49 = 100°  Something not obvious I want to touch on is that if the intake opens after top dead center, a negative value for the opening should be used. If the exhaust closes before top dead center, a negative value should be used here as well.

To start the process of checking the timing the valve clearances should be set to zero. Thicker shims can be used and zero clearance can be confirmed with a lash gauge. A degree wheel and pointer will need to be installed on the engine. There are many ways of attaching these items and each engine will provide its own challenges.

Here I’ve left the flywheel on and installed a couple washers behind the degree wheel to space the degree wheel from the flywheel. Then the flywheel nut is used to secure the degree wheel. The pointer can be made from welding rod, a coat hanger, or anything else you can find. I’ll be finding TDC with the cylinder head installed, so I used one of the exterior head bolts to secure the pointer. If you will be finding TDC with the head off, choose another location. 

Before the cams can be timed, TDC must be found. This can be done with the cylinder head on or off depending on the process you use. The piston dwells a few degrees at TDC so more accuracy than zeroing the degree wheel to the piston’s highest position is necessary. Similar to finding the cam lobe center, TDC can be found by measuring equal distances on the piston’s up and down stroke and then confirming that the degree wheel timing is equal on both sides at the measured distances. Dial indicators or piston stoppers are commonly used to do this. 

HOT TIP: Piston stoppers can easily be made by removing the center section of a spark plug and then tapping a suitably sized threaded hole in the remaining part of the plug so a bolt and lock nut can be installed. The stopper can then be easily threaded into the spark plug hole. 

Whichever method of finding TDC you decide to use, start by moving the crankshaft to the approximate TDC position. Then without rotating the crankshaft move the degree wheel so that TDC on the wheel coincides with the pointer. Next, set up your piston stops or measure piston travel on both sides of TDC. In this example I’m using a dial indicator which extends through the spark plug hole down into the cylinder. I’ve decided to take measurements at 0.050” (1.27mm) of piston travel before and after TDC. At each measurement point the number of degrees indicated on the degree wheel before and after TDC should be the same if I have found true TDC. 

If the degree wheel values don’t read the same before and after TDC determine which way the wheel must be rotated so that the values become equal. Then carefully rotate the degree wheel without rotating the crankshaft to alter the degree wheel’s position. Once altered, recheck and confirm that true TDC has been found. This can be a tedious process but is extremely important for checking cam timing accurately. Repeat the procedure for checking TDC 3 - 5 times to ensure repeatability and accuracy.

After true TDC has been found, be extremely careful not to inadvertently move the degree wheel or pointer. Do not rotate the crankshaft using the nut securing the degree wheel to the crankshaft. Instead, use the primary drive gear nut or bolt to rotate the engine over. 

Next, set up a dial indicator on the intake or exhaust lifter bucket, depending on which camshaft you are checking. You’ll have to use some ingenuity here in determining the best way to secure the dial indicator to the engine. I’ve used a flat piece of steel and secured it to the cam cap using the cylinder head cover holes. Make sure the indicator travels as parallel to the path of valve travel as possible for accurate readings. Also makes sure at least 0.060” (1.52mm) of travel from the indicator’s resting position is possible so adequate valve lift can be measured. 

Once the indicator has been set up, the cam timing can be checked. Whenever checking timing only rotate the engine over in the direction of engine rotation. Reversing engine rotation will result in inaccurate measurements due to the reversal of gear meshes and chain slack. If you miss a measurement point, rotate the engine over until you get back to the previous position. 

Slowly rotate the engine over until 0.050” (1.27mm) of valve lift has occurred. Then record the position of the degree wheel. Next, rotate the engine until the cam begins to close the valve. Once only 0.050” of indicated valve lift remains record the position of the degree wheel. Repeat this process of checking opening and closing positions 3 - 5 times to check for repeatability before calculating the cam lobe center. 

Once you are confident in your measurements proceed to calculate the cam lobe center. On the KX250F engine my intake lobe center is as follows: 

Measured Intake Open (0.050” Lift) 39 ° BTDC
Measured Intake Closure (0.050” Lift) 74 ° ABDC 
Intake Lobe Center = (( 39 + 74 + 180 ) ÷ 2 ) - 39 = 107.5° 

On my stock KX250F engine the actual lobe center is 107.5°. At this point if I had adjustable cam gears, I could rotate the gear slightly so that the lobe center corresponded to the specified lobe center value. The same procedure is followed for checking and adjusting the exhaust cam timing. Remember if mistakes are made when setting cam timing big problems can result, so it is best to be very patient and focused when performing this task. Always check your work 3 - 5 times to make sure the timing is repeatable and making sense. When tightening adjustable cam sprockets, use a locking agent and be sure to torque the bolts to their specified values. 

When working with single camshafts that have both the intake and exhaust lobes ground on them, focus your efforts on achieving correct intake timing. Correctly setting intake timing is more important since it has a larger effect on power. The intake valves also have higher lift than the exhaust valves, potentially creating clearance troubles between the piston and valve if the intake valves are mistimed.  

With your new fangled ability to adjust cam timing, you may be wondering what happens if you advance or retard the intake and exhaust cams from their standard positions? The lobe separation angle refers to the number of degrees which separate the lobe center of the intake lobe from the lobe center of the exhaust camshaft. The lobe separation angle can be calculated using the following formula:

LSA = (Intake Centerline + Exhaust Centerline) ÷ 2 

As a rule of thumb, reducing the lobe separation angle by advancing the intake and retarding the exhaust camshaft will increase valve overlap, move power further up the power curve, increase cylinder pressure, increase the chance of detonation, and reduce the piston to valve clearances. On the contrary, increasing the lobe separation angle by retarding the intake cam and advancing the exhaust cam will have somewhat of the opposite effect. There will be less valve overlap, power will move to a lower RPM, chances of detonation will be reduced, and the valve to piston clearances will increase.

The likelihood of finding more or better power by advancing or retarding the camshafts is not all that likely because manufacturers, tuners, and aftermarket companies already test specific combinations of cam timings to death. In addition, if the lobe separation angle is reduced, the piston to valve clearances should be checked to ensure they are adequate. My advice is to run the prescribed cam timings to reduce the chance of problems occurring.

Asymmetric camshaft timing can be set in a similar fashion to symmetric camshafts, however instead of focusing on the lobe center position, the specific opening and closing points will need to be measured. Timing cards supplied with asymmetric cams should have specific instructions for setting timing, but normally valve clearance is set to zero and cam positions are recorded at specific lift heights. Based on the measured opening and closing positions, adjustments are made to the timing until the timing matches the specified values.

I hope you enjoyed this exert on checking and adjusting cam timing. As always feedback is appreciated so please leave comments below. 

If you're interested in more engine building info check out my book The Four Stroke Dirt Bike Engine Building Handbook. Right now we are having a 4th of July Sale where everything on our site is 20% off with the discount code fourthofjuly2017. Just be sure to enter the code upon checkout so you receive your 20% off!  So if you've had your eye on our Four Stroke Dirt Bike Engine Building Handbook or even our Value Pack, but haven't pulled the trigger yet - go for it!
  Availabe at: DIYMotoFix.com - Paul

Paul Olesen

Paul Olesen


What Do You Love and Hate about Today's Machines?

Today I want to shift gears, open the floor for discussion, and talk about the state of dirt biking as it relates to the bikes we buy, ride, and maintain. In my relatively short existence, a number of things have happened in the industry which has been interesting to see. A few examples, which are not by any means exhaustive of all that has gone on, include the emergence of the four-stroke power plant, electronic fuel injection, improved tire technology, electric bikes, and the development of air forks. On a more micro-level we’ve seen improvements to materials, new manufacturing processes, and coating processes which have allowed ever increasing performance. As a fellow rider and someone who has no bias or stake when it comes to manufacturers and product offerings, I’d like to hear your thoughts as they relate to today’s machines. My question to you is a simple one, are your needs as a consumer being met by today’s manufacturers and bikes?  What aspects of today’s machines do you love and what are pain points for you?  If you could do things your way, what would you change? Are there machine variants that aren’t being offered?  Leave a comment below that addresses these questions or share your historical perspective! I look forward to your responses. Thanks and have a great week!

- Paul

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


How to Separate Your Crankcases The Right Way

“Splitting the cases” is often referred to as a daunting or undesirable task, but if you are well prepared and properly equipped then it can be a straightforward job. To alleviate any concerns you may have with the task, I want to discuss best practices and share some tips that you may find useful when dealing with crank bearings that utilize an interference fit with the crankshaft. We’ll get started by discussing preparatory items and work through to completing the job. Preparation I always recommend prepping for crankcase separation by thoroughly reviewing the service manual. This is important in case any special instructions are present, such as guidance on how the crankcases should be positioned. Typically, it is advantageous to lift one half off the other in a certain orientation due to the way the gearbox or other components are installed. Secondly, a review of the manual may highlight any specific hardware that must be removed prior to attempting to split the cases. From a tools standpoint, a crankcase splitter tool is a worthy investment because it will help ensure the job goes smoothly. Case splitters are relatively inexpensive and widely available. Alternatively, for the budget conscious or lesser prepared, a case splitter is something that could be fabricated. Whether buying or making, ensure you pick up a model with a protective end cap for the crankshaft or fabricate one. We’ll discuss the end cap later. The other tools required are all fairly standard and include your typical sockets, wrenches, and soft mallets. Wooden blocks or other soft semi-malleable spacers should be selected which level and raise the crankcases off the tabletop. This allows the cases to be positioned so that the split line between the cases lies horizontally and subsequent splitting can be done vertically. This will help ensure evenness of separation as well as reduce the likelihood of components falling out of the cases unexpectedly. As much as shortcuts are desirable, just about everything external to the cases must be removed in order to successfully split the cases. Clutch, stator, crank gear, etc. must be removed prior to case splitting. Your service manual will provide further clarity as to what needs to come off. Technique & Tips Once you’re ready to separate the cases, the first thing we’ll need to do is remove all the crankcase bolts. The crankcase bolts should be removed via any prescribed patterns outlined in the service manual. Since the crankcase bolts are typically several different lengths, ensuring the location of each bolt is well documented is extremely important. As I discussed in my post on keeping track of bolts, the cardboard gasket method or any other you find suitable should be utilized so that the reassembly process is straightforward later on. After the crankcase bolts have been removed, the crankcases should be inspected one final time to ensure no hardware that should have been removed prior is hitchhiking. Trust me, trying to separate cases only to find there is one last forgotten bolt is quite frustrating! Once you’re confident all the necessary hardware has been removed, position the cases on the blocks with the correct half facing up. Next, install the protective cap over the crankshaft. I advise using the cap whether you own a two or four-stroke simply because in both cases it helps preserve the end of the crankshaft. This is of particular importance on four-stroke engines that utilize an oil feed that passes through the crank. Once the crank end is protected, proceed to install the crankcase splitter. Select threaded holes that are as close to equispaced from one another as possible to promote uniform loading of the case splitter. When threading the case splitter studs into the crankcase, make sure you engage at least 1.5 times the diameter of the stud diameter. For example, if the stud is 6mm in diameter make sure at least 9mm of thread engagement length is achieved. This will help ensure the threads are not stripped when you attempt to separate the crankcases. With the crankcase splitter installed begin tensioning the main bolt against the end of the protective cap. Proceed to tighten the bolt until the crankcases begin to separate about a 1/16” (1.5mm). Once separation has occurred, make sure that separation is even all the way around the cases. Due to the way the case splitter loads the cases, the area near the output sprocket tends to lag. Case separation needs to be even so that the dowel pins used to pair the cases together don’t bind. If the output sprocket end of the cases hasn’t separated, use a soft rubber or plastic mallet to gently tap in that area. Tap carefully and only on case areas that appear sturdy. Once you’ve created an even gap, proceed to tension the splitter bolt, tap when necessary, and fully remove the crankcase. Upon separation, make sure that no gearbox components, such as washers, have stuck to the case. What I’ve described is the ideal sequence of events for a successful case separation, however, occasionally the cases won’t be as cooperative. In the past, I’ve had to deal with crankcases where moisture has found its way into the dowel pin bores and corroded the dowel pins. This effectively seizes the dowel pins in their bores and makes the separation job more challenging. If the crankcases are being resilient to separation, stuck dowel pins may be a potential problem. Most dowel pins are located opposite one another and their exact position can often be referenced in the service manual or in the crankcase section of part microfiches. Once the location of the dowel pins has been confirmed, a torch can be used to lightly heat the dowel pin areas. Heat will expand the metal surrounding the dowel pin and aid in freeing up the stuck pin bore. Usually, a few careful rounds of heat, tension on the splitter, and well-placed tapping is enough to free up the pesky cases and get them separated. Alternatively, if the heat does not help, applying a penetrant to the pin bore areas is another option that may help free things up. If you find yourself dealing with stuck cases, the key is to be patient and think through all your options. In these types of situations, most mistakes are avoidable and are usually the result of rushed decisions.    Once the cases have been separated, the remaining tasks of removing the gearbox and pushing the crank out of the remaining case half can commence. I hope you’ve enjoyed this write up on crankcase separation and that it makes you more prepared for the job. If you’ve got additional crankcase separation tips that you want to share, please leave a comment below. For additional engine building information, whether two or four-stroke, check out my engine building handbooks. Each handbook is offered in print or digital form, contains over 250 color pictures, detailed instruction from start to finish on full rebuilds, and contains a wealth of information pertaining to diagnostic testing and precision measuring.
Thanks and have a great week! -Paul

Paul Olesen

Paul Olesen


The Two Stroke Dirt Bike Engine Building Handbook is Here!

In today's post, I'm very excited to share details about my new book,The Two Stroke Dirt Bike Engine Building Handbook. As with all of my blogs and technical resources, my goal has been to bring riders clear and concise technical information. My two-stroke book exemplifies this and puts nearly 300 pages of engine building knowledge at your fingertips.

I wroteThe Two Stroke Dirt Bike Engine Building Handbook to be an all-encompassing guide on engine building. From the moment there is doubt about the engine's overall 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 relevant topics you'll encounter as you proceed through an engine build and take any guesswork out of the equation.

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 a 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, where to look for wear patterns, and shows examples of worn and damaged components.

If you're interested in making modifications to your engine or if you're curious about how certain modifications affect performance, I wrote an entire chapter dedicated to the subject. Within this chapter a discussion on how performance parts such as expansion chambers, port timing modifications, and cylinder heads alter overall engine performance is included and helpful suggestions are provided to aid you in choosing the correct components for your build, depending on your specific riding needs.

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 nearly 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. As a way to thank you for your support, we're offering TT members 15% off during a special TT pre-sale which runs from now until December 5th (when the book officially launches). Simply follow this link to learn more and order: ThumperTalk Pre-Sale

Thanks again for all your support as we've grown DIY Moto Fix from an idea to a thriving community of riders who are passionate about making their machines perform better through their own hard work. Thanks for reading and have a great week. -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


How The Two-Stroke Exhaust System Works

In my last post, I shared details about how the two-stroke cylinder works, in today's post I want to provide an overview of how a performance two-stroke engine's exhaust system works.
Adding a performance exhaust system can be a great way to increase power and/or alter the power delivery of an engine. I would also argue that optimizing a two-stroke engine’s exhaust system is equally as important as ensuring the cylinder’s ports are correctly designed for the given application. Not all exhaust systems are designed to do the same things, and much like cylinder port design, exhaust designs are intended to alter power in specific ways. Having a basic understanding of how an exhaust system works can go a long way when it comes to selecting the right exhaust pipe for your engine.

Two-stroke exhaust design is complicated and there are many different variables that must be considered when designing a pipe. I don’t intend to go into all of them, but I will share a few of the most critical.
  Each time the exhaust port opens to release spent combustion gases, pressure pulses are created. Modern pipe designs harness this pulse energy and use it to help scavenge and fill the cylinder. The process starts when a positive pressure pulse is created once the exhaust port opens and combustion gases leave the cylinder. The positive pulse travels down the pipe until it reaches the diffuser, at which point part of the pulse is inverted and reflected back towards the cylinder as a negative wave. This negative wave is very beneficial in pulling spent exhaust gases out of the cylinder and fresh mixture up through the transfer ports. The remaining positive pulse continues on its journey towards the end of the pipe where it encounters the reflector. The reflector acts as the name implies and forces the positive pulse back towards the exhaust port. Once reflected back, the pulse remains positive and, if the pipe is designed correctly, will reach the exhaust port just as the piston is about to close off the port on the compression stroke at the desired RPM for maximum power. Any fresh mixture which has escaped out the cylinder will be forced back in by the positive pressure pulse.

The tuned length of the pipe is dictated by the exhaust port timing, RPM of max power, and the speed of sound. Pulse length and amplitude are governed by the angles of the diffuser and reflector. Generally, steeper cone angles create pulses with more amplitude but shorter duration. Shallower angles generate pulses with less amplitude but longer duration. Given these variables, it is easy to see how a pipe could be tailored for specific applications. An engine converted for road racing may utilize a pipe designed for peak power which incorporates steep diffuser and reflector cone angles so that pulse amplitude is not sacrificed. This peak power would likely come at the expense of a narrowed range of power. An engine tailored for woods riding may feature a pipe with shallower cone angles, resulting in less pulse amplitude, but a broader spread of power.  

The last parameter I want to touch on is how the tailpipe, which is sometimes referred to as the stinger, influences the pipe. The tailpipe creates a flow restriction in the pipe which allows the pipe to have a certain amount of back pressure. Enlarge the tailpipe and the back pressure decreases, make it smaller and the back pressure increases. As back pressure increases or decreases, so does temperature and ultimately the speed of sound. As the speed of sound changes, so does the resonance RPM of the pipe. If the tailpipe is sized too small, cylinder scavenging will be inhibited. When this happens, the cylinder, fresh mixture, and piston will all be overheated.

While engineers and tuners can estimate starting pipe dimensions and tuned lengths, a great deal of trial and error testing is usually still necessary to fine tune the exhaust pipe and optimize the design. Unless you intend on building your own exhausts, this work will have already been done for you. When selecting an exhaust system, you need to focus on how the exhaust alters the power curve. Exhaust systems are tailored to deliver more bottom end performance, top-end performance, or performance throughout the power curve. Selecting which system is right for you will depend on how you want your engine to perform. If you’ve chosen to modify your cylinder ports, installing an exhaust system that compliments the porting can be very beneficial. You might be wondering about slip-on mufflers. If you’ve followed along with my explanation of how exhaust pipes work, you’ll notice I made no mention of the muffler. While the muffler can have a small effect on performance, it is not the primary factor. Upgrading a muffler is a good way to reduce weight, but there won’t be a slip-on out there which significantly increases power, in the same way, a properly designed expansion chamber can. I hope you enjoyed this write-up on key features affecting the performance of two-stroke cylinders. As for Two Stroke Handbook news, we received our first printed proof of the book this week! Needless to say, we are inching closer and closer to an official release date. To stay updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to sign up, see the new cover, the Table of Contents, and some sneak peek pages right from the book. Thanks for reading and have a great rest of your week! -Paul

Paul Olesen

Paul Olesen


Everything You Need To Know About The Two-Stroke Cylinder

This week I want to talk about two-strokes. To kick off this post I have some awesome news. The Two Stroke Dirt Bike Engine Building Handbook is off to the printers and will be available for pre-sale very soon! Getting the book off the ground has been no cake walk. It's been two years coming and we are so thankful our riders and fans have been patient with us! At the end of this post I'll give you instructions on how you can stay updated on the launch. With that said, let's get started. Today's post aims to provide an overview of the important aspects of the two-stroke cylinder and answers a couple commonly asked questions relating to cylinder modifications.  

The ports found within a two-stroke cylinder in combination with the exhaust system have the greatest influence on power, torque, and the RPM at which maximum power is created out of the various engine subsystems found within a two-stroke engine. Typically when a new engine is designed the port characteristics are one of the first parameters to optimize. With this being the case they are also one of the first things anyone planning on altering an existing engine should consider improving or tailoring to their specific application. A two-stroke cylinder consists of exhaust, transfer, and occasionally inlet ports (true inlet ports are only found on piston or rotary valve controlled engines). The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. The cutaway of the cylinder shown details the port arrangement and common nomenclature.

The inlet port/passage delivers air into the engine’s crankcase, most commonly through a reed valve, on a dirt bike engine. On older engines, a rotary valve or the piston may also be used to control the opening and closing of the inlet port. On modern machinery, the inlet simply connects the reed valve to the cylinder or crankcase. In this case, the primary restriction in the inlet port is the reed valve and as such the valve’s geometry and flow capabilities often dictate the inlet port's performance.

The transfer ports are responsible for moving fresh air and fuel up from the crankcase into the cylinder. This occurs as the piston travels downward after the cylinder has fired. Once the piston uncovers the tops of the transfer ports the blowdown phase is complete, at which point much of the exhaust gas has been expelled from the cylinder. As the transfer ports begin to open, the exhaust pipe sucks fresh mixture up through the transfer ports into the cylinder. To a lesser extent, the downward motion of the piston also aids in creating a pressure differential between the crankcase and cylinder. The shapes and flow capabilities of the transfer ports play a big part in how effectively the cylinder can be scavenged of exhaust gases and filled with fresh air and fuel. The transfer ports also help cool the piston. The exhaust ports dictate how much and how well exhaust gases depart the cylinder. Similar to the transfer ports, the duct shape, angle, length and volume have a large influence on how well gases can flow through the port. Typically, dirt bike engines commonly feature bridge port or triple port designs.

General insights into a cylinder’s performance can be made by characterizing attributes such as the timing of the exhaust and transfer ports, the port widths, and the directional flow angles, but a deeper analysis is required to truly optimize a cylinder. Today, tuners and designers rely on computer software which computes a port’s specific time area (STA). As defined in the EngMod 2T software suite, “STA provides an indication of the effective port window area that has to be open for a certain length of time to allow enough gas to flow through the port to achieve the target power at the target RPM for the given engine capacity”. STA values are used to quantify the exhaust, transfer, and inlet port geometry as well as the blowdown phase of the two-stroke cycle. The blowdown phase occurs between exhaust port opening and transfer port opening and is one of the most important parameters in predicting engine performance. By manipulating STA values and subsequently the height, shape, and size of the exhaust, transfer, and intake ports, an engine’s power characteristics can drastically be altered. Port modifications can be made which allow more air to move through the cylinder, ultimately increasing the power of the engine. Conversely, ports can be filled or welded and reshaped which tame the engine and provide less peak power but a broader spread of power. Simple modifications to the ports can also be carried out which improves the air or exhaust gas flow through the port yielding better cylinder scavenging.

Can I modify my own cylinders?
Unless you have a deep passion for two-stroke tuning, are willing to spend money on software and porting equipment, and are comfortable throwing away botched cylinders, I would recommend having a reputable professional carry out any desired port modifications. Experienced tuners have developed a number of porting combinations that will work well for various makes/models and riding applications which will take the guesswork out of the situation and provide you with a good performing cylinder.

Who should consider two-stroke porting modifications?
For the sake of simplicity, I will lump porting modifications into two categories: major and minor. Major port modifications would include tasks such as significantly changing the port timings (by either removing or adding material), altering the shapes of the ports, or changing the directions the ports flow. Anyone drastically altering their engine, such as turning an MX engine into a road racing engine, should consider major porting modifications. Other examples of applications that may require or benefit from major port modifications include drag racing, hare scrambles, ice racing, or desert racing.
  Minor port modifications would include basic tasks such as removing casting flash, slightly altering the ports to achieve the stock port timing, and correcting areas that result in minor flow deficiencies. Just about everyone could benefit from these types of corrective actions; however, if the engine is already performing or producing adequate power, they often aren't considered.  I hope you enjoyed this writeup on key features affecting the performance of two-stroke cylinders. To stay officially updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to see the new cover, the Table of Contents, and some sneak peek pages right from the book. Thanks for reading and have a great rest of your week! -Paul  

Paul Olesen

Paul Olesen


DIY Piston Ring Compressor

Today I want to share a quick tip with those of you who are working on your own engines but just can’t justify buying a set of piston ring compressors. It’s entirely possible to make a perfectly good ring compressor from materials you can get at the hardware store. All you need is some plumber’s pipe hanging tape and a hose clamp that is sized according to your cylinder bore.

To construct a DIY ring compressor from plumber's pipe hanger tape you will need to determine the length of tape required. This is easily done using the following equation for calculating the circumference of a circle. Length of Tape Required = Piston Diameter x π (Pi) When the tape is wrapped around the piston tightly, the final length may need to be reduced slightly so that the ends don’t butt together. Once the tape has been cut to length, make sure whichever side of the tape will be contacting the rings is smooth and free of little plastic burrs that could catch the rings.

Simply lube up the tape, tighten down the hose clamp, and you are in business.

Do you have a tip that makes compressing rings easier or cheaper? If so, leave a comment below! - Paul

If you enjoyed this tip and want access to more like it, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. On the fence about the book? Check out what other riders are saying: Thumper Talk Review

Available at: Amazon.com DIYMotoFix.com  

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


New and Re-plated Cylinder Prep

Today I want to share some pointers on preparing new or re-plated cylinders that will help ensure your engines run stronger and last longer. Plus, I've got an update on the two-stroke book I've been working on that I'd like to share. Let's get started!

A Universal Concern
First, both new and re-plated cylinders must be cleaned prior to assembling. Normally the cylinders will arrive looking clean, but looks can be deceiving. I have no doubt that the factories and re-plating services clean the cylinders as part of their processes, but I highly recommend cleaning the bores a final time prior to use. Shown below is a new Yamaha cylinder that I extracted quite a bit of honing grit out of.

If left in place, the honing grit will ensure that the piston rings will wear out faster than they need to, so be sure to take the time to properly clean new cylinders prior to assembly.

What’s the best way to clean the cylinder bore?
Start by using warm soapy water and a brush to clean the cylinder. Take your time and be thorough.

After the majority of the honing grit has been removed switch to automatic transmission fluid and a lint free rag for one final cleaning.   As a test to check cleanliness, rub a cotton swab against the cylinder bore. If the swab picks up any debris and changes color, your cleaning duties are not over. The swab should be able to be rubbed against the bore and remain perfectly clean.
  Two-Stroke Port Dressing
For two-stroke owners, the second item I want to bring to your attention is port dressing. Port dressing is a term used to describe the process of deburring/breaking the edge at the intersection of the cylinder plating and the ports in the cylinder. During the plating process, plating usually builds up excessively at the edge of the port and must be removed after honing. Proper removal is critical to ensure acceptable piston ring life.

Manufacturers and plating services will break the edge in different ways and to different magnitudes, which ends up being a whole other topic. The important thing is to ensure that any new or re-plated cylinder you use shows visible signs that the port edges have been dressed. A dressed port edge will be easy to spot because it will feature a different surface finish than the cross-hatch created from honing. This is easily visible in the image shown above. Many port dressing operations are done manually so some irregularity in the geometry will usually be present. If there is no visible edge break on the port edges, I would be highly suspicious and contact the service that plated the cylinder or sold the cylinder and confirm with them if a step was missed. Typically a chamfer or radius in the .020 - .040” (0.5 - 1mm) range is used. Two-Stroke Power Valves
Lastly, it is possible that some of the power valve components, such as blades or drums, will not fit correctly on cylinders that have been replated. This is because the plating can occasionally build up in the slots or bores where the power valve parts reside. Prior to final assembly, be sure to check the function of the power valve blade and/or drums to ensure they move freely in their respective locations within the cylinder.

If plating has built up in a power valve slot or bore, it will need to be carefully removed. To do this, appropriately sized burs for die grinders or Dremel tools can be used. If one is not careful, irreversible damage to the slot or bore can result. When performing this work proceed cautiously or leave it to a seasoned professional. Burs for the job can be difficult to track down in stores, but are readily available online from places like McMaster-Carr. When purchasing burs, be sure to pick up a few variants, such as rounded and square edged, designed for removing hard materials.

The Two-Stroke Book
From February to March we photographed the entire book. From April onward we have been formatting and proofreading. Needless to say, we are in the final stretch! If you want to stay updated on the moment the Two-Stroke Dirt Bike Engine Building Handbook is ready for pre-order, sign up at the link below. We can't wait to get this book out the door and into your garage.
  Sign Up for Updates on the Two-Stroke Book Thanks for reading and have a great rest of your week!


Paul Olesen

Paul Olesen


Four Stroke Cylinder Head Reconditioning

It's time to open up a can of worms and talk about a hotly debated topic in the powersport community - four stroke cylinder head reconditioning best practices. I've perused the forums and had discussions with people about reconditioning four stroke cylinder heads and there appears to be a lot of mixed opinion and beliefs on what is right or wrong. I'm certainly not going to say my take on the subject is the only way, but I do want to share my opinion, explain the technical details, as well as touch on the machining process. The text below is out of my book, The Four Stroke Dirt Bike Engine Building Handbook, and details why cylinder heads should be reconditioned a certain way.  Whenever new valves are installed in a cylinder head, it is best practice to recut the valve seats since the valves and seats are mated parts, otherwise the new valves are very susceptible to premature wear when run in the old seats. If a major overhaul is being performed, there is a good chance that enough seat wear will have occurred during the engine’s life that the valve seats will need to be recut before new valves are installed. This may be news to you, so I want to provide an explanation of why this is necessary. 

The term concentricity is used to describe the relationship between the axis of two circular objects. When two objects are perfectly concentric, their axis match up precisely with one another. In the case of the cylinder head, the valve guide axis and the valve seat axis must be as close to perfectly concentric as possible and parallel to one another. Usually, guide to seat concentricity is kept around 0.001” (0.025mm) or even less for racing applications. This is achieved by the factory by using a manufacturing process where the valve guides are reamed first. Then the freshly reamed valve guide bore is used to center the valve seat cutter. Once centered, the valve seat is cut. This process is then repeated for all the valves and results in very good concentricity between the valve guides and valve seats. As the engine is run, the valve guides, valve seats, and valve faces will wear. The valve guides will wear from front to back in an oval shape at the top and bottom of the guides. In a cross sectioned view the valve guide will take on an hourglass shape. The guide will become oval as a result of thrust forces stemming from the way the camshaft contacts the lifter bucket or rocker arm. These forces are transmitted to the valves and cause the valves to thrust against the sides of the guides, eventually causing the guides to become oval shaped. Once the guides start to become oval shaped, the valve faces will no longer be as concentric to the valve seats as they originally were. When this happens the valves will start to slide against the seats, causing the seats and valve faces to wear. The valve seats will eventually become out of round and the sealing between the valve face and seat will suffer. Installing new valves into oval shaped guides and out of round seats will ensure that the new valves wear out very quickly!

To ensure the new valves being installed last as long as possible, the cylinder head’s seats and guides must be reconditioned once they are worn out. Complete cylinder head replacement is always an option, but I want to focus on freshening up the original head which is usually a more economical option, but comes with many more variables surrounding the quality of the job.

There are numerous services offered in the marketplace for valve seat cutting, however, not all valve seat cutting methods are equal in terms of quality. There are hand operated seat cutters, dedicated seat cutting machines, and a few other options to choose from. Selecting the correct seat cutting process and entrusting the work to a competent engine builder is very important. The valve seat cutting process should mimic the OEM process as closely as possible. A concentric valve seat will never be able to be cut without first servicing the valve guides. If the valve guides are out of round then they will either be reamed to a slightly larger size if they are not too oval in shape or they will be replaced. Once any issues with the valve guides are addressed and they are perfectly round from top to bottom, it will be possible to cut the valve seat. Ensuring the valve guide is perfectly round is extremely important since the valve seat cutter is centered off of the valve guide bore.

Cutting the valve seat concentrically to the guide requires a combination of skill and using modern machinery. The best valve seat cutting equipment in the world is worthless without a good experienced operator running it. There are two main factors which make cutting a seat concentric to the valve guide difficult. To start with, the valve seat cutter uses a pilot which locates in the valve guide. Since the valve stems are very small in diameter the pilots used to guide the seat cutters are also very small in diameter. A small diameter pilot shaft that centers the cutting tool can flex easily, which presents a real problem when cutting the seats. The next issue that arises when reconditioning seats is that often times the cutting tool will try to follow the path of the old valve seat which can make it hard to cut a concentric seat. Couple these factors together with slop within the machine, setup error, and operator error and you can see how quickly things can come out of alignment and you can end up with a poorly cut seat. In addition to seat concentricity, the depth the seat is cut to will influence valve spring pressure, shim sizes, and the compression ratio of the engine. All three of these variables will be reduced the deeper the seat is cut, which is not a good thing. The surface finish of the seat itself will influence how well the valve seals. A seat with chatter marks or other machining blemishes will not seal as effectively as a smooth seat. The valve seat width and the contact point between the seat and the valve face are also very important. Due to the complexities involved with cutting valve seats on modern four-stroke dirt bike engines, the job should not be left up to just anybody. There are numerous businesses which specialize in valve seat cutting which have both the right equipment and expertise to do the job correctly. I highly recommend spending some time researching and finding a reputable cylinder head machining company when it comes time to recondition your head. If the cylinder head must be shipped off in order to do business with a reputable company, the additional wait will be worthwhile. If you found this information helpful and would like more technical info on maintaining your four stroke engine, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. Thanks for reading and happy wrenching! As always if you have comments or want to share your thoughts please leave a note below.


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Paul Olesen

Paul Olesen


Maintenance Readiness

I hope you all have been out riding and enjoying spring. I got back into the hare scramble racing scene over the weekend after a three year hiatus and had a blast. Today, I just want to share a quick tip and start a discussion on preparatory things that help shorten the time it takes to do complex maintenance tasks, such as rebuilding an engine.

Quick Tip
Prior to turning a wrench carefully look over the service manual scanning through all the applicable procedures and subsystems. If I’m working on an unfamiliar model, I find it is helpful to jot down a rough outline of the disassembly sequence. This saves me time in the long run as I don’t have to rely as heavily on the service manual or continually flip through various sections. Another option is to use post-it notes to bookmark each relevant section in the manual. Mark the post-it notes with numbers or headings so you know where to turn to next. Earmarking or bookmarking the torque tables is also a huge time saver no matter the task. 

Be sure to scan through the manual as well to identify any specialty tools that are required that you may not have.

Discussion Points What other preparatory things can be done to help speed up the major maintenance process? Is there a method to your madness or do you dive right in? Thanks for reading!



Paul Olesen

Paul Olesen


Help! - Bike Only Starts When Pushed

Today I want to talk about a situation I hear all too often. Someone’s bike, whether it be a two-stroke or four-stroke, only starts when it is pushed.

Before I discuss potential causes for this scenario, take a moment to think through the situation yourself. What mechanical factors would result in either a two-stroke or four-stroke only starting when it is bump started?

In either case, the reason the engine is able to start when it is push started is because it is able to build more compression than it otherwise could when it is kicked or the electric starter is engaged. More compression is achievable because the cranking RPM is higher than what’s possible with the aforementioned starting methods. With a higher cranking RPM for a four-stroke, more air will fill the cylinder on the intake stroke, and for a two-stroke the scavenging process will be improved. With this being the case we must look at reasons why the engine is struggling to build compression in the first place.

Starting problems specific to four-strokes:
1. Valve seat recession - When a valve seat wears out and recedes, the valve moves up towards the camshaft. This leads to diminished valve clearances and if left to run its course, the valve and shim will bottom on the camshaft’s base circle. This can prevent the valve from seating and make the engine hard to start. 2. The valve is bent - A valve with a serious bow to it may get jammed up inside the guide and not return all the way back to its seat. Bent valves typically result from an over-revved engine where the valves contact the piston. Valves can also bend to a lesser extent if they were mated to valve seats that were not cut concentrically to the guides, or they were paired with worn seats.

3. The valve stuck in the guide - This is usually due to the engine overheating. When the engine overheated the clearance between the valve and guide diminished which caused metal to transfer from one part to the other, ultimately ruining the surface finish on one or both parts. Once this happens the valve may be prone to sticking in the guide until the engine warms up. 4. The valves and seats do not seal well - Worn valves and valve seats can compromise the seal between them. Valve and seat wear is a natural part of running an engine but can also be accelerated by ingesting dirty air.

Starting problems specific to two-strokes: 1. The reed valve is worn - Reed petals that don’t close all the way, are chipped, or bent will not allow sealing of the crankcase and efficient gas flow up from the crankcase into the cylinder.

2. An engine seal or gasket has failed - A two-stroke engine requires a well sealed crankcase and cylinder in order for it to scavenge gases efficiently. A worn crank seal, leaky base gasket, or problematic power valve seal can all make starting more difficult. Two and four-stroke problems: 1. The piston rings are worn - Worn piston rings will allow compressed gases to escape past them. 2. The head gasket or o-rings are leaking - Usually a leaking cylinder head will be accompanied by white smoke if coolant is being pushed into the combustion chamber, by coolant being blown out the radiator, or both.

I hope you found this rundown of potential problems useful for diagnosing bikes that like bump starting over a kick or the push of a button. Can you think of any other problems that would lead to lack of compression? If so, leave a comment and share them. If you liked this post and want more technical info, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. In it you will find over 300 pages of technical knowledge to help you get off on the right foot when rebuilding!

- Paul
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Paul Olesen

Paul Olesen


Three Easy Ways to Improve Engine Cooling

This month I want to discuss three easy ways to improve engine cooling for your dirt bike or ATV and explain why they are effective. As improvements are made to an engine that increase its power, the amount of heat the engine will create will also increase. Effectively removing heat from the engine and cooling it is very important as the power output of the engine goes up. The cooler an engine runs, the more power it can produce. There are three ways that the aftermarket attempts to improve the cooling system of a particular engine. 1. Increase flow through the cooling system. 2. Increase the cooling capacity of the radiators. 3. Increase the pressure of the cooling system. Let's dive in. 1. Increase flow through the cooling system
The flow through the cooling system can be increased by installing a water pump impeller designed to increase the flow rate of the coolant. The reason increasing the flow rate of coolant works is because the rate of heat transfer from the engine to the cooling system is directly proportional to the mass flow rate of coolant. This is thermodynamics jargon, but there are two key parts to consider. First, how much coolant is flowing, and second, at what speed the coolant is flowing. The more coolant that flows and the faster it flows will reduce the temperature difference between the point where the coolant enters into the engine and where it exits. This next part is not quite as intuitive. When the temperature difference between the inlet and outlet is reduced, the average coolant temperature is lowered. When the average coolant temperature is lowered the engine will run cooler. This is why fitting a water pump, which increases the flow of coolant through the engine, improves cooling. 2. Increase the cooling capacity of the radiators
Radiators consist of a series of tubes and fins which run from the top to the bottom of the radiator. These are often referred to as the radiator’s cores. As coolant enters the radiator it moves through the series of tubes and heat is transferred from the coolant to the fins. Air passes over the fins and heat is transferred from the fins to the air. This transfer of heat from coolant to air is how radiators reduce the temperature of the coolant. Coolant temperatures can be reduced by upgrading radiators in three ways, by increasing the frontal area of the radiators, by making the radiators thicker, or by using materials with better heat transfer properties for the cores. For all practical purposes, increasing the radiators’ frontal area and improving the core materials is rarely a viable option for dirt bike applications. This is because there is little room for the radiators to begin with and they are susceptible to damage, making the use of expensive core materials a risky affair. Unfortunately, both of these options are better improvements to make before resorting to increasing the thickness of the radiators. Increasing the thickness of a radiator is not as efficient of an improvement as increasing the frontal area of the radiator. In order for thicker radiators to cool more effectively than their stock counterparts, airflow past the radiators is key. When the thickness of a radiator is increased, air must travel a greater distance through the radiator before exiting. The speed the air is traveling plays a big role in determining how quickly the air heats up as it moves through the radiator. If the air is not traveling fast enough through the radiator, the air temperature will rise and equal the coolant temperature before reaching the end of the radiator. Once this happens, heat transfer stops and whatever portion of the radiator remains will not help with cooling. In order for a thicker radiator to be effective, air must flow quickly enough through it so that the exiting air temperature is at, or better yet, below the coolant temperature. In conclusion, benefits from adding thicker radiators will be more prominent in applications where speeds are relatively high. Whereas in applications where the bike is hardly moving, improved cooling may not be noticeable. 3. Increase the pressure of the cooling system
The last alteration to the cooling system that can be made is to install a high pressure radiator cap. As coolant temperature increases, pressure increases inside the cooling system. The radiator cap is designed to be the pressure release point in the cooling system in the event that too much pressure builds up. This can occur as a result of overheating or a blown head gasket for example. By designing the radiator cap to be the weak link in the system, other parts of the system, such as seals, don’t end up getting damaged from being over pressurized. The radiator cap features a plug and spring on its underside. The spring is designed to compress once a certain pressure is reached, at which point the plug will move upwards and uncover a pressure release hole where excess pressure will be vented.

The coolant’s boiling point and ability to conduct heat are necessary factors in understanding why a high pressure radiator cap can help improve engine cooling. Water alone boils at 212°F (100°C) while a 50/50 mix of water and antifreeze boils at 223°F (106.1C). Radiator cap pressure designations are usually advertised in bar, with most stock radiator caps designed to withstand pressures up to 1.1 bar (16psi). The more pressure a fluid is under, the more difficult it becomes for the fluid to vaporize, and the higher its boiling point becomes. When water is under 1.1 bar of pressure, the temperature water will boil at is 260°F (127°C) while a 50/50 antifreeze mix will boil at 271°F (133°C). By installing a radiator cap designed to withstand higher pressures, an additional increase in the coolant’s boiling point will be seen. High pressure caps are usually designed to withstand 1.3 bar (19psi) of pressure. This 0.2 bar (3psi) increase in pressure over the stock system will increase the boiling point of water or antifreeze by 8.7°F (4.83°C). This will then bring the boiling point of pure water or a 50/50 antifreeze mix to approximately 269°F (132°C) and 280°F (138°C) respectively. While this small temperature increase alone won’t do a lot for your engine, coupling a high pressure cap and using coolants with better heat transfer properties can do wonders. Antifreeze (ethylene glycol) alone is not an inherently good conductor of heat. In fact, pure antifreeze conducts heat about half as well as water, while a 50/50 mix of antifreeze and water conducts heat approximately three quarters as efficiently as pure water. This means a cooling system using a 50/50 mix of antifreeze would have to flow faster than a cooling system filled with pure distilled water in order to achieve the same cooling efficiency. What this means for you is significant cooling gains can be made by using distilled water and an additive called “Water Wetter” in place of an antifreeze-water mix. Water Wetter is an additive that improves water’s “wetting” abilities (another whole subject), adds corrosion resistance, and slightly increases the boiling point of water. A high pressure radiator cap in conjunction with distilled water and Water Wetter as the coolant is by far the best route to go for high performance applications where freezing is not an issue. For applications which must still be resistant to freezing, the antifreeze-water ratio can be altered in favor of mixtures incorporating more water than antifreeze so that the cooling efficiency of the mixture is improved. Just bear in mind the freezing point of the mixture as it is thinned with water will be reduced, so you will need to pay close attention to the environment you are operating in so that the coolant is never susceptible to freezing. A frozen coolant system can ruin an engine and makes for a very bad day! I hope you enjoyed this post on three easy ways to improve your engine’s cooling.  One more thing before I wrap up! April is Autism Awareness month, and here at DIY Moto Fix we couldn't be more excited to announce that we will be donating 15% of all profits made in April to AutismMX. If you haven't heard of AutismMX, this amazing non-profit brings Autism awareness to the motorcross community. Founder, Matthew Dalton, created this non-profit after finding that motorcross was an amazing way to connect with his autistic son. At DIY Moto Fix this non-profit also touches a chord with us. Our filmmaker and photographer, Kelsey Jorissen, loved dirt biking with her autistic brother throughout their childhood. The Autism MX Project focuses on four areas: Autism MX Day Camps are days for ASD kids and families to have the chance to ride AMX’s little dirt bikes and quads and enjoy the sport of motocross. Team Autism MX Sponsoring amateur MX racers, riders as well as sponsoring AMA pro racers. Through doing so, they are getting out the word on Autism Awareness to millions. AMX Puzzle Piece Apparel from shirts, graphics, goggles, to help stand out and support Autism Awareness. AMX Ride Days for Autism Awareness AMX celebrates Autism Awareness and is a fundraiser for The Autism MX Project. So for the entire month of April - if you buy a book, a video, even a poster - 15% of that purchase will go towards AutismMX and their amazing cause. Thanks for reading and have a great rest of your week!

Paul Olesen

Paul Olesen


What Spare Parts Do You Bring To The Track or Trail?

With warmer weather and the riding season around the corner for many of us, I wanted to cover a topic that can either make or break an event. Whether you’re competing in a racing series or traveling to the track or trail, let's talk about event preparedness. More specifically, what spare parts should you keep on hand? Plus, what methods do you use to keep your spares organized?

Honestly, I struggled with organization until I started working on this post. I had no method to my madness. Every time an event came up I’d do the same thing; throw a bunch of stuff in a box or the back of my van and head to the event. The sad part is I now realize this was a weakness of mine for quite some time, but didn’t do anything about it! Maybe you can relate?

I finally said enough is enough. I don’t throw my tools in a cardboard box when I go to a race, leaving what I bring to the fate of my memory. So why would I do that with the spare parts I bring?

I started solving this problem by compiling a spreadsheet detailing what spare parts I keep on hand for ice racing and hare scrambles. I realize that each discipline will differ and may have niche parts that should be kept. The goal here is not to definitively define what spares one should keep on hand, but to have a conversation and provide a resource that can be used to help people get set up based on their own needs.

Once I took inventory of everything I felt I wanted to bring to a race, I went to Menards and went hunting for the perfect organized storage bin/toolbox. Here’s what I ended up with:

Naturally, once I returned with the toolbox, my list grew and I probably need to go back for a bigger one. I intend to store a copy of the spreadsheet in the tote so I can keep tabs on inventory and know exactly what I have available.

Should I get another bike, this system is easily replicable and my plan is to get another organized toolbox that goes with it.

This system is how I went from being an unorganized “throw it in the van at the last minute” rider to a more relaxed well prepared rider. I’d love to hear how you handle event readiness, what you bring, and how you keep track of it. My hope is that by sharing our strategies we’ll save someone the misfortune of having a bad day at the track or trail. Perhaps I'll even end up with more things I need to add to my list.


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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 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 Keeps Track? - Ride Logging

Do You Keep Track? How many of you regularly keep track of the number of hours or miles that have accumulated on your engine since the last time you performed any type of service on it? How helpful would it be if you had a designated place to log any riding, maintenance, and suspension tweaks? Between riding and maintenance there is an awful lot of stuff to keep track of. The last thing I want to do is complicate the matter any further by having to try and remember in my head when the last time I did some work on the bike was. So what is the best way to keep track? Having a simple ride log/service sheet is a great way to keep track of your machine’s maintenance and stay ahead of any potential problems. Another awesome device to pick up for your machine is an hour meter. Hour meters are great since they only record actual engine running time, which gives you a more realistic time value than estimating how long your engine ran while you were out on your ride. I wanted to share with you the log I use to keep track of the time I put on my bikes. Click this link to download a free copy. I have set up three versions, one for Excel users, one for Google Docs users, and a PDF that can be printed for the folks that like to document their riding on paper.   Shown below is an example of the log I keep for my YZ250. The log is simple to use and helps document basic settings, maintenance, and engine run time. I like to keep track of location and weather conditions so I can document any variation in engine performance. This is particularly useful for carbureted machines since jetting is dependent on temperature and atmospheric conditions. Once you start to build a database of information you will start to notice trends that emerge based on where you are riding and the temperature. These trends will help you determine the proper jetting for given conditions more quickly and save you a large amount time in the long run. Keeping track of any maintenance you do on the bike along with the number of hours on the engine is a no brainer. Not only will this Ride Log help you determine when certain services are coming up, it will be a major confidence boost to a potential buyer concerning your maintenance of the bike if you ever decide to sell, and ultimately help you retain a good resale value. The suspension column I will use occasionally if I make a minor tweak, however the bulk of my suspension documentation goes into a suspension log. I added this column for those of you who do not change your suspension too often. I am going to discuss suspension logging with all of you coming up soon so stay tuned. I hope that you find the rundown of the riding log beneficial and that you decide to start keeping track of your riding to improve your maintenance practices! Keep in mind I tailored this to as many of you as I could. If you want to customize it for your specific discipline, feel free. Once you get into the habit of keeping track of these things you will end up taking better care of your machine and ultimately save yourself a huge chunk of time and money in the long run. 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


Help Moto Mind Help You + A Quick Tech Tip

I hope you all had a good holiday season and are excited for 2017. The ice bike has been kicking my butt so far, but I’m thankful I’ve been able to get out and ride. I’m definitely excited for the new year and today I wanted to discuss my upcoming blogs and share a quick tech tip with you.   My blog post pool is low right now and I’d like your help! Looking ahead to 2017 I want to deliver informative posts tailored to what you need to know and want learn. In the comments section below be sure to share your thoughts on what you’d like to learn about this year. Whether it’s maintenance, tuning, suspension, two-stroke, four-stroke, or anything else-- I want to hear what you have to say.   Depending on post length it takes me anywhere from 2 - 5 hours to write a piece I feel comfortable publishing for you, so I want to make sure I’m spending my time covering topics that are truly beneficial and relevant.   Moto Mind Quick Tech Tip
Anytime you drain fluids from something you’re working on and halt progress (think waiting for parts) tag the throttle or any other visible location and note that there’s no fluid in the machine.   This isn’t always applicable but here’s an instance of when it was. I’ve moved a few times in the last couple years and during that transitional period my bikes were five hours away in northwestern Wisconsin. One weekend I was set to make the trip back home to go riding, certain that my bike was ready to go. I got there and found that I’d left myself a tag noting that I was only part way through the oil change I so vividly remember completing. While I usually check my sight glass anyway, I can’t say I always do, especially if I’m in a hurry. Whether or not I would have caught the lack of oil without the tag I will never know, but I’m just glad I left myself a visual reminder.   If there’s something you’d like to learn about, please leave a comment below and I’ll see what I can do to work it into this year’s blogging schedule!   Plus, if you got socks or other stuff you didn't want over the holidays, be sure to check out my book and treat yourself!   http://www.diymotofix.com/books.html   Amazon   - Paul  

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


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 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