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yz400fsmasher

is the stroke the same on a 98 yz400f as a yz450f?

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im asking this because i wanna get a big bore kit for my 400f and i cant find one anywhere but see them for the 450f all the time. if anyone knows let me know.

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Get a 426 crank, then check out LukesRacing.com and look into their 444 kit. Several people on here have nothing but praise to say about the kit.

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no, the 450 has a longer stroke and a different size wristpin....and im told there are other differences in the crank. For me, Im just looking for a 450 engine to swap!

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Another advantage of the 426 crank swap is the piston pin size is bigger and hence better reliability if you add a larger bore piston.

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Try Lukes and Eric Gorr for big bore kits. I believe the 400 punches out to only 420 cc's. As posted above, you can get a 426 crank (with larger wrist pin) and get out to 444. I love mine. Note that if you do that, you will need to get a new primary drive gear as well...

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