New valves, small shim size.

2 replies to this topic
  • KennyS212

Posted November 05, 2012 - 08:02 AM


I adjusted the valves a couple of times on a 2006 yz450f. Being that they were needing more frequent adjustment I decided to send the head out and have all new stainless valves installed. (New seats, springs, retainers and valves) When I received my head back I proceeded to set the initial valve clearances and ended up needing 1.35mm shims on all 3 intake valves and 1.65mm shims for both exhaust valves. My assumption is that the seats were not actually replaced resulting in the need for such thin shims. Should I bother trying to have something done or just go with it?

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  • etuke

Posted November 06, 2012 - 08:10 AM


maybe they cut the seats effectively moving the valve and stem up in the head further and that would require smaller shims.

  • grayracer513

Posted November 06, 2012 - 10:44 AM


If the seats were in fact finished properly, and you have the correct clearance, run it. I think you can get either Honda or aftermarket shims small enough to adjust a normal amount of run in, if it happens.

With steel valves, we used to shorten the tops of the stems slightly so as to compensate for the valve moving up when the seats and faces were done. The valve grinding machines have an attachment for that purpose. Not certain, but I assume you can't do that with Ti valves due to hardness issues.

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