I have a question on custom engine work???

1 reply to this topic
  • DavidAchziger

Posted December 17, 2008 - 06:02 PM


I have a 2000 Yz426 and I have a bad top end and need new cylinder and head. So my question is my friend has a 2004 Yz450f complete top end but bottom end is bad, I was wondering if I can take the top end off the Yz450f the cylinder and head and valve train and put it on the 2000 Yz426 when I put the cylinder on it all looks like it will bolt on just fine. The piston is the same size the only thing that is different is the bore stroke the yz426 is 95.0x60.1 mm (3.74x2.37in) and compression ratio is 12.5:1
The 2004 yz450f is 95.0x63.4 mm (3.74x2.50in.) the compression ratio is also 12.5:1 and if I was to switch the top end I would not have to have a compression relase cable I would have the auto compression on the exhaust cam. So I was wondering if I could machine the cylinder or the head down enough to make up the difference of the stroke I dont see why this would not work if I could do this I would save a lot of money. If anyone thinks this might work or might not work please let me know any advise would be very helpfull. Thank you very much.

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  • matt4x4

Posted December 18, 2008 - 12:54 PM


your stroke is where you get your compression from, also your CC's, if you mill the head down 3.3mm you changing the CC.c of the bike by about 5% and who knows what your compression will be - it may stay close to 12:1
Then there's issues such as cam guides, cam chain length (closer to crank gear now so it/they might become a custom items)
It may work, but it sounds like an expensive way to find out that it doesn't...

Just thinking that it'll likely be cheaper to just go and get a fresh bottom end for the 426......they're not that expensive...


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