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

Paul Olesen

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.”


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. 


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


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