Will a YZ426F head and piston fit on a YZ400F

[maltisecross]

I love my bike but I am looking to upgrade my motor a bit. I was just wondering if I get a 426 head and piston, would it just bolt on to a 400? Any input on this would be great.

[1rkcooper]

I believe it will bolt together.

This should answer your questions.

http://www.powroll.com/P_YAMAHA_YZFWR426F.htm

[kylwk1500]

you should be good to go. As long as you are doing the complete top end. The bottom end should be virtually the same besides possible gearing differences.

[grayracer513]

you should be good to go. As long as you are doing the complete top end. The bottom end should be virtually the same besides possible gearing differences.

Not so. Review the info at the posted link, and you will see that using the 426 cylinder requires a 426 piston (obviously), and that that in turn requires the use of a 426 rod, because the 426 wrist pin is bigger.

The crank has to be rebuilt with a 426 rod and big end in order for that to work.

[Birdy426]

You also will not see a big performance increase from a head swap. The 400 and 426 heads are virtually identical wiht the exception of the vacuum nipple for the octapus hot start on the 400s. The 426's had the 2nd gen FCR that has hot start internally.