98-99 wr400 engine in 01 yz426?

3 replies to this topic
  • niterider40

Posted March 26, 2008 - 04:11 PM


I just found out the engine is basically shot and I found a wr400 engine for 600 bucks. Does anyone know if I can use this wr engine in my newer yz? at a loss up here in alaska.

  • Birdy426

Posted March 26, 2008 - 10:08 PM


Yes, you can. Save your 426 carb and use it (it's mo-bettah). You will need to plug the vacuum port on the l/h side of the intake runner on the 400 head. Tap it for a 6mm screw and plug it up that way. Use the 426 header so you don't have to remove the header to change the oil filter. Get the 400 ignition box, as they may be different. Time the camshaft to YZ specs (search this forum to find out how). Tranny ratios will be significantly different.

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  • Alternative

Posted March 27, 2008 - 12:17 AM


I think the '98 WRs had a smaller diameter swingarm pivot than the '99+, meaning the rear engine mounting bolt will be a different diameter if the engine you get is a '98. You can just bore the hole out bigger for the bigger pivot, other than that should be no problem.

  • niterider40

Posted March 27, 2008 - 01:21 AM


It sounds pretty simple even if I need help I could probably do that. How long do you think that would take a beginner type mechanic like me? I should get a 400 manual too and really learn more and read this site more. thanx


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