426 Valve Adjustment Help.

3 replies to this topic
  • underground-mpyre

Posted July 08, 2014 - 05:21 AM


Talked to the previous owner of my 426 last night and he mentioned he has never did a valve adjustment ever. My friend on here with a Wr400 said it needs to be done every 500 miles, is this correct?

I did a search and couldn't find a sticky link on how to do it properly and when to do it. Any help is a appreciated in finding the proper link.

  • grayracer513

Posted July 08, 2014 - 08:42 AM


I had an '03 that I never adjusted the for more than 3 years and nearly 300 hours.  I did, however, check them 5 or 6 times over that period.  My '06 has gone well over that, and had a top end replaced, but only one valve replaced, and two others adjusted.  If you find them in spec, no need to adjust anything, right?


Normal wear conditions cause the valve clearance to get smaller over time, so noise isn't an indicator, and unless the bike starts showing symptoms of tight valves (low compression, hard starting, "lean" idle symptoms that the idle fuel mix can't address), there won't be anything that stands out screaming that you need to adjust them.  Just do it every once in a while. 


The process is shown in the manual:




...and gone over here:


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  • underground-mpyre

Posted July 09, 2014 - 07:24 AM


Thanks for your awesome help!


Has anyone ever thought about a YZ hotcam into the top of the motor while you were in there?

  • Pooley

Posted July 22, 2014 - 12:15 PM


500 miles between valve checks is a bit overkill, but it can't technically hurt.  I just checked my valves about an hour ago on my 2001 WR426 and I was 0.20 mm on all exhausts, and 0.10 mm on all intake valves.  This is the minimum clearance but still in specs.  This bike has somewhere around 13-15k miles of Michigan singletrack, with no roads or dualsport of any significance.  I will be adjusting the valves for the first time this weekend in an effort to troubleshoot starting issues, which is more likely to be rings due to poor compression.


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