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.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • 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?

Related Content


2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies

Help with 2000 yz426 by weekend woods racer

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  36 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.