01 yz426 valve clearance mininum. Adjust?

2 replies to this topic
  • Dennish87

Posted May 31, 2013 - 06:44 AM


When I checked the valve clearance on my yz426 they were at the minimum or just a fuzz larger. That was before the rebuild. I am replacing the springs, seat, piston and timing chain. I will remeasure them after I get it all put back together but if they come out at minimum again should I shim them to get it closer to the middle of the spec or leave them where they are and check them in say 5 or ten hours. I don't beleive they've been shimmed before. It looks like it has the factory shims in them now. They only say the measurement, no manufacturers marks like hot cams or anything. If memory serves me, all 3 intake are at .004~5 and both exhaust at .006~5. "~" equals approximation. I also noticed that the spec for my bike has been revised in the "Supplement" section in the back of the Clymer manual. Any help would be appreciated. It will save me about 85 bucks on an already mounting bill to restore my bike.



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  • grayracer513

Posted May 31, 2013 - 08:08 AM


.004" is in specification for the intakes, so no, you shouldn't change that. Yamaha sets up all their new heads as close to minimum specified clearance as they can get it.

However, the spec for the exhausts is .008-.010", not .006. Better double check that.

  • Dennish87

Posted June 01, 2013 - 08:35 PM


Yeah, I looked back at what I wrote for the exhaust SPEC and it was at
.008 like you said. Do you think my clearances will change after installing new valve springs? Ill obviously check them but just curious.

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