98 yz 400f with a wr400 bottom end

4 replies to this topic
  • Nelson24

Posted November 05, 2015 - 05:30 AM


I picked up a YZ 400f and the bottom end needs a rebuild. I found a 99 wr400 bottom end with very low hours. Can I use my top end from my 98 YZ on the WR case? I know the piston kits are different. Not sure how compatible these are. Thanks guys.

  • grayracer513

Posted November 05, 2015 - 07:53 AM


The piston kits are interchangeable.  Yamaha lists both engines as using the same piston, rings, clips, and pin, showing old part numbers for each.  The two lower ends/top ends are also interchangeable, and apart from the transmission gear set and the magneto assembly, they are almost completely identical.

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  • Nelson24

Posted November 05, 2015 - 09:00 AM


Thanks for the clarification! Do you recommend I swap anything from the yz 400 and put in the WR? The case and the crank are no good in the yz400. Everything else is there.

  • grayracer513

Posted November 05, 2015 - 09:33 AM


It will have more power using the YZ cams, head and carb.

  • Yz400fthrashr

Posted November 06, 2015 - 11:58 PM


Hey grayracer,do you know what other model kickstarts would fit my 99yz400f?

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