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Old 06-06-2017, 09:38 PM
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Can someone confirm if a 2002 yz250f cylinder will fit a 2008 motor?
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Old 06-06-2017, 09:51 PM
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Yes it will bolt up, but there are differences. The 2002 does not have the auto decompression , but rather a manual decompression system which creates differences in the casting and thus some extra holes that will need to be filled. You would also need to use the 2008 exhaust cam in the 2002 head. I know the exhaust cams from as late as 2006 were a straight drop in on the 2001 and 2002, but I am not 100% sure about the 2008 cam. I would suggest that you find a 2006 to 2008 head for this build as the 2002 was not as good in the performance department.

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Last edited by PawPaw; 06-07-2017 at 05:13 AM.
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Old 06-06-2017, 10:10 PM
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Thanks for the info and quick reply!
The specific scenario is as follows (since I think it affects most of the fitment differences you brought up):
I'm eyeballing a 2008 yz250f to assemble and flip. The owner has the bike apart because the crank seized. I have a friend with a 290 big bore kit in the box but it's for a 2002. Since it seems there a chance it fits, let me see if he can give me the manufacturer name and call their tech support up to try to get a definitive answer.
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Old 06-07-2017, 05:10 AM
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I guess I must have misread your question as I was answering as it pertains to the cylinder head only and not just the cylinder.
With that stated, the cylinder should fit. I would check the piston wrist pin size between the two I seem to recall there was a change and thus the big bore piston & pin may not fit your 2002 crank & rod, but my memory is a bit fuzzy.
As I recall the pistons are the same for 2001 to 2004, then 2005 to 2007 were different and then 2008 was different and I think this was due to the pin size.

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Old 06-07-2017, 09:36 AM
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Thanks for the good info. The big bore kit seller searched and found that the part number is the same for '02 and '08. So it looks like it will fit... now I just have to convince the wife...
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Old 06-09-2017, 09:00 PM
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I might be interested if the price is right , and it's in good shape ....
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Old 06-09-2017, 10:13 PM
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I haven't pulled the trigger on it yet. I had a quad brought over with a seized engine and have also been holding off to check on a local CRF. By any chance do you have a Yamaha flywheel puller (for the YFZ/YZF)??
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