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potman1980

yam wr cylinder swap

3 posts in this topic

hi there,

i'm about to start what i think will be a serious project, but i'm a little stuck on the dimentional side of things.

i'm trying to build a 450 motor using a 400 short stroke bottom end and 450 head and cylinder.

i'm not sure if you van fit the wr/yzf 450 cylinder onto the 400/426 crank case, or failingtht can the 426 cylinder be bored out to 98mm from the 95mm STD.

i will be posting pics of the project as i go on the yamaha wr section if anyone is interested in watching the progress.

thanks for any help in advance.

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Given the fact that the largest kits that were ever offered for the 426 were 444cc kits, (97mm bore) I would doubt that it's safe to run the 426 cylinder out to 98. A 450 can be bored to 98, however. IF you can stand a 450 cylinder on the 400 crankcase (I have heard you can, but the source is unreliable), and you were to do that, you'd end up with 452cc. IMO, it's a long way to go for 8cc more than you'd get with a 444 kit.

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I have a 400 bored out to the 444 and I love it. The next step that I am aware of, is you can get the crank stroked a additional 2mm which I think brings you to around 468 cc. The place I saw the does the stroking of the crank is http://www.powroll.com/P_YAMAHA_YZFWR426F.htm

I haven't worked with them or heard any feedback on them, so you may want to research them a little or give them a call.

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