07′ CRF250R Engine Rebuild – Bottom End

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Year, Make, Model:

In this video & blog post, the 2007 Honda CRF250R is covered. Similar years include 2004, 2005, 2006, 2008, & 2009.


Service manual

I’ve uploaded the full 400+ page service manual which covers the bottom end as well. The Owner’s manual only covers the top end and valve adjustment. I’ve uploaded both since you can never have enough resources.

Right click link and select “save as” if you are having loading issues.

Honda CRF250R 2005 Owner’s Manual & Competition Handbook

Honda CRF250R 2007 Owner’s Manual & Competition Handbook

Honda CRF250R Service Repair Manual 2004 2005 2006 2007 2008 2009 61KRN05



This CRF stalled going into a corner and was difficult to restart. After limping it back to the pits, it failed to restart and engine became seized. The oil filter was removed and full of metal shavings gold in color. The picture below shows all the shavings in the filter and on my hand. The large end of rod & crank pin is where the failure occurred. The cases have to be split and a new crank assembly will have to be installed.

CRF250R brass gold shavings oil filter crank bearing


Work area prep

This job will require a clean and large work area. Clean your workbench of other projects, and organize your workspace, it will save you time and frustration in the long run. Make sure to thoroughly clean your CRF before disassembly, you don’t want debris falling into your fresh engine! Print the appropriate sections from the service manual, and head over to Rocky Mountain ATV and print the part diagrams. The part diagrams give you a nice exploded view which is helpful for reassembly. Also, I like to highlight what parts need replacing during disassembly, that way you are less likely to forget to order that one part! Another tip: take pictures or video as you disassemble, it will help if you hit a roadblock during reassembly. I referred to my own video for the reassembly process numerous times.



Aside from basic hand tools, you will need a flywheel puller and clutch holder tool. You will not need a case splitter, you can simply tap the case halves with a rubber mallet to split them.

Tusk 24mm flywheel puller

Tusk clutch holding tool

Autozone OEM PN 27119 Bearing & Race Installer (Free rental)


So how long did it take?

It took me roughly 12 hours to complete the job. Plan on spending 2 hours to pull the motor out of the frame.  My camera batteries died on me while pulling the motor, so the video really focuses on the motor only.


Parts cost

OEM parts were used and purchased from Rocky Mountain ATV/MC. Here is a list that includes PN and cost:

Rockymountainatvmc.com - Dirt bike & ATV parts

Bearing, Special Roller



Bearing, Radial Ball (30 X72 X16)



Oil Seal (38 X52 X7) (Arai)



Oil Seal (39 X56 X7.5) (Arai)



Oil Seal (20 X33 X5) (Arai)






Ring Set, Piston (Std)






Pin, Piston



Clip, Piston Pin (16 Mm) x 2



Gasket Sheet Kit B



Gasket Sheet Kit A



Parts Grand Total: $488.94



Valve shims – Where to buy individual?

You can purchase individual shims (7.48mm) from Rocky MTN here.


Add Your Comments

If this info has helped you get your CRF get running again, or have any questions, please comment below.


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  1. brandonNo Gravatar says:

    Thanks VERY much for posting the service manual!

  2. DrewNo Gravatar says:

    Thanks for posting all this information! I bought a 2007 crf250r with a blown engine and completely rebuilt it using this info. All in all I got a crf with a fresh engine all for a pretty good price!!

    • MatthewNo Gravatar says:


      Awesome! Now go have some fun with it. I was actually riding this bike on Sunday, I ride faster on it than my KX250!

  3. rickNo Gravatar says:

    Thanks very much for sharing your resources and taking the time to post such a useful set of videos.

  4. chris boydNo Gravatar says:

    Just got an 05 Honda …the engine was rebuilt but was rebuilt poorly …. Looked for some info on this bike and found your YouTube vids and the manuals ….Just want to say thanks man !!!! Not afraid to twist wrenches and I like to know specifics before I start a project … Your info helped hugely …again thanks for posting man !!!!

  5. Landon PNo Gravatar says:

    Hey thank you for the great video. I went on to Cheap Cycle Parts to find the exploded diagrams of the engine for my 2004 crf250r but was wondering what the difference is between CRF250R A (4M000001-) and CRF250R A/A (4K050001-) Thanks

    • MatthewNo Gravatar says:

      Those numbers relate to your VIN #, apparently they must have changes some PN’s in the middle of a production run. You can compare both and verify if the same PN’s are called out for the parts you need. Hope this helps.

  6. John DixonNo Gravatar says:

    Hej Matthew, what a great guy you are. Max my 14 year old son bought a 05 model with a completely stripped engine, (with my guidence). We now begin the rebuild. He will learn heaps and a great process for us to do together (not the first time). Thanks so much. Kiwi boys down under in New Zealand.

  7. aaron pierceNo Gravatar says:

    WOW! Thank you so much. I bought a 06 crf250 that had a blown motor (just like your video) Brass in the oil filter. The kid had so much money into this bike, and it was pushing 40 HP. I bought it for 1000 and was going to part it out, but now Im thinking, this old farm boy can put 500 dollars into it and have a very nice bike to ride with my yz450!!!

    • MatthewNo Gravatar says:

      Nice! Definitely tear it down and see what it needs. Hopefully the cylinder is in good shape.

      • aaron pierceNo Gravatar says:

        As I inspect the left and right cases. I see the oil pump housing has been pretty scarred on both left and right case. Enough to catch your fingernail on .. I think It will really effect the oil pressure. So both cases need to be replaced on my build.. bummer, there goes my savings on doing it myself. But on a good note, tranny,cylinder, and head look look great.

  8. Landon PNo Gravatar says:

    Hello I was wondering if you would know why the left crankcase cover on my 2008 Honda crf250r has little specks of missing metal? I dont think it is from rock chips because I have not seen any other crf250r that has the damage. Could it be heating up too much?

  9. joshNo Gravatar says:

    Help! My name’s josh just had my 08crf rebuilt top an bottom. I got it seized for $1000 and got an extra motor seized with it ,I found that the extra motor was original. But the cases where gone ,so I rebuilt the one in it. Thinking it’s 04_07 motor. I just payed $500 for the valves to be done , it all runs great except when I put in gear an let clutch out I get some go, but a lot of r.p.m.I bought new clutch kit. Same result, changed basket off the 08 it looked New no or very little wear.and got same result what else could it be? Please help!

  10. josh129No Gravatar says:

    Hey thanks for responding so quickly.so like I said the top and bottom were rebuilt we used hot rods crank oem piston New seals and bearing. Put the clutch basket pressure plate etc. from the 08 motor to the rebuilt one prob 04-07. Starts first kick and sounds good but the clutch is awful. When let it out u don’t get any grab til levers almost out at best if I adjust it, it won’t go at all.when I do get goin prob only 15 to 20 max. New clutch plates fibers springs same thing. Switch out any clutch components I could to find a solution. Clutch shaft everything what else can this be??

    • MatthewNo Gravatar says:

      Josh, download the service manual and take a look at page 11-2. The clutch pack has changed after 07′ with the addition of 2 spring plates that go in forst. Also, go to an online fiche finder to see if other parts have the same PN as your year.

  11. DennisNo Gravatar says:

    Thanks, now i know how to remove the flywheel, i dont think there is one single video on youtube that shows how to remove it on the CRF, but now i know how it works! cheers!

    Three questions!

    Do i have to remove the flywheel to change the cam chain?
    And how do i check the cam chain are in good condition?
    If second question is hard to answer: how often do you recommend to change it? ive heard things like every piston change..

    • MatthewNo Gravatar says:

      Yes, you have to remove flywheel to remove chain.

      I don’t know how to check the chain. Sometimes the service manual states to measure “X” amount of links to measure stretch. I did not see it in this manual.

      Change it with every top end. They are $20-30, pretty inexpensive to just go ahead and change it IMHO. Also check tensioners for wear.

      A worn chain will not allow timing marks to line up properly and also retard cam.

  12. allyNo Gravatar says:

    Hey I have a crf 250 2006 model going to a shop to get rebuilt and I have the crank piston oil pump gasket kit everything is mint just need a rough idea how long a full bottom end and top end rebuild takes last time I was 1800 so most stuff has no wear atoll?? any idea on price many thanks ally

    • MatthewNo Gravatar says:


      The motor rebuilt in the video took me about 8-12hrs to rebuild IIRC.

      I can’t speak for how much the shop is going to charge you, especially since you live in a different country. They should be able to give you a ball park before you even bring your bike in.

  13. Stephen MorrinNo Gravatar says:

    Hi, thanks for your very informative video. I was just wondering if the engine and gearbox oil mix in these engines? I am looking at using one of these engines for a different application and I would like to use the engine only so I may have to invent a coupler to bolt directly to the flywheel. If possible I could then remove the gear clusters.

    Would this be possible do you think?

    • MatthewNo Gravatar says:


      The engine and gearbox oil do not mix.

      If you are going to frankenstein this motor, you will have to use the RH side crank output. The LH side cover has all kinds oil passages that actually uses the crankshaft to flow oil.

      May I ask what you are building?

      • Stephen MorrinNo Gravatar says:

        Thanks very much for your reply. I am looking to use the engine to drive an electrical generator and using the heat from the cooling system to heat a small building. What components are behind the RH crank cover? With the fact the the oil systems are separate would it be possible to remove the internals from the gearbox and just keep the casing do you think?

        Thanks again,


        • MatthewNo Gravatar says:


          I think it would be cheaper short term and long term to select a briggs and stratton type motor for this application. The CRF motor is a race motor that requires quite a bit of maintenance. For example, do you want to adjust valves every 6-10hrs or replace top end every 20hrs?

          • Stephen MorrinNo Gravatar says:

            For the system I am designing the engine would only need to run at 1500rpm, not at top end so I figured that rebuild time could be extended considerably as a result. I’ll check and see what water-cooled B&S type engines there are though. Thanks for the info

          • MatthewNo Gravatar says:

            If you do use the CRF engine, I would use a higher RPM, since these motors do not lug well that low.

            The specified idle RPM for these motors is 1700-1900.

  14. AndrewNo Gravatar says:

    Hello, there is a 08 Crf250r for sale. $1000 the bottom end is bad it is locked up. The owner has 2 good cranks to go with it about 40 hours on them both. It has a fresh top end and new valves.The tires are good and everything else is good. is this bike a good deal for the work ill have to do to it and Money i will put into it? Thanks, Andrew

    • MatthewNo Gravatar says:


      Keep in mind that if the crank blows it can damage the top end. Also, do your research on what a good used bike sells for (maybe around $2500 or so). Lastly, what is 8-12hr of your time worth? Hope this helps.

  15. AndrewNo Gravatar says:

    Will 2008 cases work on a 2007

    • MatthewNo Gravatar says:


      I searched on the parts finder and cases & gaskets have different part numbers for those 2 years. So no, I don’t think it will work.

  16. EricNo Gravatar says:

    Hey Matt I’ve watch your rebuild twice and it has amazing attention to detail. You used only oem parts. My 07 seized on a trail ride and I am planning on doing the rebuild using a wiseco kit. What are your thought on the brand? Also my bike was able to be freed while rocking the bike in gear but still found shaving in my oil. Am I still into a full rebuild?

    • MatthewNo Gravatar says:

      Hi Eric,

      Thanks for the compliments! I really appreciate it.

      I always try to use OEM parts whenever possible. I realize aftermarket can save on cost. I personally don’t have any experience with aftermarket kits for this model. You can try googling “wiseco vs hotrod” for tons of info on the subject.

      If you found shavings, it’s time for a new crank. Do not run the engine any longer, more damage will result if it locks up, especially at higher RPM.

      Good luck with the rebuild and let me know if you have any more questions.

  17. CraigNo Gravatar says:

    hi Matthew

    I have an 06 crf250r and need some help figuring out what I need to do to get it up and going again but any how this is what happened somehow the air filter had been taken off without my knowledge and came back from a vacation and went for a ride. a few miles down the dirt road I notice somethings not right. look behind me and all I seen was white smoke I shut the bike off and pushed it back home. cant get it to start now and I can push the kick starter down with only two fingers. im thinking its going to need a complete break down and rebuilt from the bottom up but im not shur iv never rebuilt any kind of motor before. so if u can I need some advice on what to do thx

  18. BeauNo Gravatar says:

    Hey mate so I was riding my crf250 2007 today, just came back from honda after getting the valves done, it went there full of oil, so I didn’t even think about checking it. Anyways i was humming along today then it stop back wheel locks up kick start won’t move so I left it what should I do and does it need a rebuild or what just so many question running through my head

  19. Will JohnsonNo Gravatar says:

    Hi matt. Great vids mate. Im not mechanically minded but am going to try fix my bike using some of your advice. Firstly is there alot of difference in setup between a 250 & 450. Ive bought a second hand ’06 CRF 450. The guy I bought it off said it had just had a top end rebuild but was missing the decom plunger, decom shaft & cam sprocket. Is this to tough a job to do for an amateur? I have the manual but it doesn’t have much in regards to this topic. Any help would be appreciated.


  20. Will JohnsonNo Gravatar says:

    Cheers for the response mate.
    Do u think I will be able to takr the kick start off and go through the clutch or will I have to take the engine out and go from there?

    • MatthewNo Gravatar says:

      Will, everything you mentioned can be accessed by removing the valve cover. The engine can stay in frame.

  21. NicholeNo Gravatar says:

    I cannot get the repair manual to download.
    Any ideas? Thanks

  22. JeremyNo Gravatar says:

    Within the next week I will be begin the same exact process with the same bike as your videos. I am thankful for the videos you have posted. Hopefully they will minimize my issues.

    Should there be much of a difference if I go with a wiseco complete top and bottom end kit instead of OEM parts?
    I feel the need to stay away from the OEM crank being as it failed after 20-30 hours.

    • MatthewNo Gravatar says:

      Hey Jeremy,

      I can’t comment on aftermarket parts and their quality. We used OEM since the parts guy in town hooks us up.

      Good luck and feel free to ask any questions.

  23. ShaneNo Gravatar says:

    Hey man, So I’ve gone through these videos and done a complete rebuild on a 07 crf250r with the same exact failure. I got everything put back together and tried firing it up and the motor felt as if it was lacking compression and all I got was a backfire. After checking the timing again and looking at there videos I became aware that there is a timing mark on the flywheel as well, going back and checking I have discovered that the flywheel marking and the marks on the right side are not exactly in line…..
    With that being said and from all I can think of….I am assuming that the gear that lines up on the right side of the case must be out of line. From my understanding the flywheel can only go one way therefore the other side is wrong….

    Any insight will be greatly appreciated, I’d like to know more before I start tearing it down again.

  24. ShaneNo Gravatar says:

    Okay I’ve gone over my cam again and believe it is right, It is lining up with the 2 flywheel marks correctly.

    If Im understanding correctly then if those 2 are lined up then the ting should be correct?

    The mark on the right side of the motor is just a hair off from matching the left side, is that something I need to worry about?

    I was very slow and meticulous when assembling the motor so I don’t feel as if I put the on the right side a tooth off, but us that a possibility here?

    I’m just trying to cover everything before I button it up again and attempt starting it.

    • MatthewNo Gravatar says:


      Yes it can be a hair off, about half a tooth max. Afterall, you can adjust a half a tooth out.

      If you double checked all your timing, make sure the decompression mechanism is OK and then try firing it up.

  25. ShaneNo Gravatar says:

    Alright, I have made sure I am at TDC on the compression strokeand all the timing marks are lined up. I tried starting again and still nothing. I checked the valves last night, this is my first time with valves, my exhaust sides are approximately at .009 and the left intake at .003 and right intake at .000
    Is it safe to say that’s why Im not starting?
    If the intake is not closing all the way would that cause me to not have as much compression as I should?

    • MatthewNo Gravatar says:

      Since you are at zero clearance, who knows how far open the valve is. Buy the proper shims, get it in spec, and try to fire it up.

      And yes, an open intake valve will not allow engine to build as much compression.

  26. TylerNo Gravatar says:

    Having trouble loading the service manual for the crf250r. But I would like it. Can you help me out?

  27. WilliamNo Gravatar says:

    Thanks for the video. I had two questions:

    1) Would I be able to use this video to fix a CRF450r?
    2) Do I need any special tools? (other than screw drivers, wrenches, socket set)

    Thanks for the help.

  28. AlexNo Gravatar says:

    Hi Mathew, my crf250x had shavings from the stator (alternator), would this require a whole new rebuild do you think, or just clean up and replace with new stator? Thanks.

  29. Andrew 114No Gravatar says:

    Can you replace valve seats twice my head had new seats put in it with over sized valves well when the head was being rebuilt the shop ordered factory size valves and tried cutting to seats to work and ruined them and now saying I need new ones but was told if you replace valve seats more than once they will fall out just trying to get some insight

    • MatthewNo Gravatar says:


      I don’t see why you can’t replace the valve seats. Maybe they meant that they can’t be cut again and you have to replace them?

  30. Andrew 114No Gravatar says:

    They said they don’t like changing seats more than once bc they are pressed in and have a chance falling out

    • MatthewNo Gravatar says:

      Andrew, I can’t provide any more insight. I don’t do any machine work so I can’t answer your question. Maybe call around and get a second opinion.

  31. BrandonNo Gravatar says:

    Great site, and I appreciate the videos and information you’ve provided.

    Quick question:

    The chain came off my 07 CRF250R and knocked a small hole in the left side crank case. Obviously, I’ll be replacing the case. Should I replace all the bearings and oil seals, as you did, or should I keep the originals; provided I see no obvious signs they need replacing?

    I do plan on replacing the piston and rings. Any other suggestions?

    I’ll be buying your video also. I saw it on youtube before you were charging for it, and it inspired me to do the job myself.

    • MatthewNo Gravatar says:


      Thanks for the compliments!

      How many hours do you have on this bike? Has the crank ever been replaced?

      I would replace all oil seals, crank, piston & rings, cam chain, and any bearings that fail inspection.

      Crank failure is very common on this model, so just replace it as preventative maintenance.

      • BrandonNo Gravatar says:

        Not many hours, probably around 20-25.

        I plan on selling the bike. I just wanted to get it running good. I can handle throwing in some new bearings and seals for preventative maintenance but not sure I want to dish out 300 for a crankshaft.

        Thanks for the info Matt!

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