Sticky Valve 2007 yz 450

During the winter season is when I do my big maintance. last winter I checked the valve lash (all was good), a couple of months later I kicked it over and there was no compression.:smirk: thought about it and decided to try to pop start it think that rapid succetion would free up the valve and it did. Rode all summer:ride: Now this winter as I'm checking my lash (2 maybe 3 need to be reset), 1 of the exhaust lifters doesn't rise completey, it does compress some but doesn't return fully aprox. .100" short. It was stilling running strong on the last ride nothing unusual was noticed. What might be causing this ? The motor hardly has 190 hours total run time. I guess will try to popstart it again to see if that works again. I don't really look forward to pulling the head, but if I do may as well replace the the piston and rings too, while I'm that for into it. I got a "REKLUSE CLUTCH" this Christmas to put on, but the down side is that i won't be able to popstart to resolve the issue next time. My guess is that it is time to fix it. Anybody had or know of this proplem?:busted: THIS INDOOR WEATHER IS BORING. ASKING FOR SOME INPUT B) THANKS

The cause of a valve that does not close all the way, or has excessive clearance could be:

  • A burr or ledge at the top of the lifter bore, often caused by a seizure of the camshaft.
  • Carbon or rust on the valve stem or face.
  • A bent valve.

I did have to popstart it today, and got it started after a long push. I think that I will pull the plug and give it a shot of WD next year and see to it that it is at top dead center (all valves closed) before I let it set for the winter. I let it idle long enough to say that it was warmed up and checked the lash again and all was well. Those two that had excess clearance were only over by .001 anyway. So I'd hope to say that maybe it was maybe a little rust. Wondering if I should still break it down (for now it is not broke)? What would somebody else do

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now