06 YZ450F just checked valves, should I adjust them?

4 replies to this topic
  • BMuu

Posted November 18, 2011 - 04:29 PM


I just checked my 06 YZ450f valves and I got

Intake .10mm .11mm and .09-.10mm this one .10mm is a little more on the snug side and the .09mm feels about right, I was able to slide in a .13mm on all 3 and it was very tight but it was noticably tigher on the last one.

The stock specs say .10mm to .15mm is good

Exhaust .20mm and .21mm

Stock specs are .20mm to .25mm

I'm sure I could just assemble it as is but would it be better to shim them closer to .13mm intake and .23mm on the exhaust? Will I notice any difference?

I can move some existing shims around to get these numbers and will only need to buy 2 assuming my dealer offers a 182 honda one.

  • grayracer513

Posted November 18, 2011 - 05:27 PM


Just for reference and scale, the entire adjustment range, .10-.15mm, is the difference between .004" and .006". And .01mm is .0004", less than half a thousandth.

If the .09mm slides in freely and the .10 drags, leave them alone. That's probably where they were set at the factory. BTW, you can shove the .13 in there, but you're opening the valve to do it. If it really is .09mm, then it's out of spec, and should be adjusted. Personally, I would favor using shims in .025 increments so as not to open them up to the high limit, but that's your choice. Where specs are concerned, in is in, and out isn't.

Likewise the exhausts are fine as they are. The tight side of the spec is better for several reasons.

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  • BMuu

Posted November 18, 2011 - 08:28 PM


Thanks! You're the one who I was hoping would reply.

I will measure the suspected .09mm one again tomorrow and see if I feel it is actually .09mm or .10mm. I can actually throw a 185 in there if I feel it for sure is .09. Currently is a 186 shim.

I know the light "drag" feel a feeler should have when measuring but it's difficult with the bend of getting the gauge lined up in there.

And you are correct, these are the factory shims/valve job. The P/O never checked them and he was the original owner.

  • RiderX

Posted November 18, 2011 - 10:20 PM


The "light drag" feel can get a little hard to decipher when bending the feeler gauge to get it in there. I work up from something you know has no drag, and work your way up. That way I know what "no drag" feels like, so I can subtract it from the "light drag", LOL.

  • BMuu

Posted November 19, 2011 - 01:19 PM


It still feels border line, the .09mm drags and the .10mm fits but has more drag than the other 2 intake valves so I'm going to drop it to a 185 pad (186 installed now)

This will make all the intake valves the same and within spec.

Thanks for the tips!

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