2008 YZ450 trouble with valves.

Normally I wouldn't be too concerened. When I first checked mt valves after the breakin period I had to shim the intake valve next to the cam sproket from 180 to a 190,thats right two shims bigger after only a short time riding. Yamaha paid for the shim but I had to do the work. Not a problem. I put less than 20 hours on the bike last season.I just checked my valves again and I had to go another size shim on the same valve (190 to 195) the rest of the valves are the same as the last check that I did. At least it is not going tight. I am thinking that the valvestem might be mushrooming....Maby.

I was just wondering if anyone else is having this problem with their 08' 450. Yamah has a good history with valves in these bikes.

Something wrong there. Talk to your dealer. That valve is bad, right now. If your information is accurately presented, I'm inclined to think it was defective (poorly coated, not coated, or the seat wasn't finished right). Convincing the dealer or Yamaha of this may be more difficult.

At this point, given the facts here, you should be OK with replacing just that one.

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