Here's the story. I have an 03 yz 450 that I bought in 06 and the bike has been nothing, but great. I've had no major issues but I don't ride the bike very much. In the past 5 to 6 years I've maybe put 60 hours on the bike. I don't get a chance to ride much.
Last year when I took my bike out to the Arizona desert and it was noticeably much easier to kick start. The bike however ran great with the only exception being in 4th gear the bike seemed to be missing with a jumpy sensation like it wasn't firing right and not being near the rev-limiter.
I checked my valve clearances this morning before work and the intake valves and exhaust valves were all .05 mm tighter below spec for each. I was surprised to that all the valves were .05 tighter with no variance and was wondering if this was normal? From the posts I've read its seems people only have one or two valves that are off spec or valves with different variances? The cams looked good and the dots lined up with the TDC and the top of the head and the cam chain seems to be tight? I plan on putting all the valves back within spec near the tight end, but was wondering if this could be a cause of compression loss as the valves should be shut tighter if I understand correctly? Everything I've read regarding the issue seems to talk about valves being loose and open causing loss of compression during kick start. I've maintained the basic maintenance of changing the oil, air filter, etc, but this is the first time I've opened the engine up.
Time for a possible top end rebuild? I unfortunately do not own a leak down tester, but may be investing in one shortly. Any suggestions?
Edited by Joel_D1124, March 06, 2012 - 05:43 PM.