Valve adjustment questions .



2 replies to this topic
  • jackiefresh69

Posted October 20, 2015 - 11:49 PM

#1

Hello guys. Bought an 2008 yz450 and I have a few questions. I've rebuild a fair few of these bikes but first time adjusting valves. Now I am confused as to why nearly all of my valves are too tight except for one valve being way to loose
Specs are : intake 10-15 . Mine are at .25 , .7 and .12
Exhaust spec : .20-.25 . Mine are .17 and .13.
My question is understandable most are tight but why is one of them loose? Is that normal?
And how far out do they have to be before it because a pain to start. This one takes at least 30-40 kicks before it does.
Thanks guys!

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  • grayracer513

Posted October 21, 2015 - 06:40 AM

#2

The normal wear pattern is to see them tighten as material wears from the valve face and the valves move farther up into the head.  

 

There are 3 common reasons for a loose valve:

 

  • It's bent (you would have little or no compression along with this)
  • Carbon on the stem or seat is holding it off the seat (again,l ow compression)
  • The stem cap has shattered, mushroomed, or broken off.  Remove the bucket and shim and check the top of the stem.


  • jackiefresh69

Posted October 21, 2015 - 12:17 PM

#3

The normal wear pattern is to see them tighten as material wears from the valve face and the valves move farther up into the head.

There are 3 common reasons for a loose valve:

  • It's bent (you would have little or no compression along with this)
  • Carbon on the stem or seat is holding it off the seat (again,l ow compression)
  • The stem cap has shattered, mushroomed, or broken off. Remove the bucket and shim and check the top of the stem.

Thanks for the reply. It seems to get good compression and and once warm it starts in a few kicks and runs like a rocket . I'll do some more inspecting today. Cheers





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