2010 YZ450F Timing Issues

[noslo98]

I am having some issues on a 2010 YZ450F that I recently had to install all new valve train and a top end on. The issue is when I set the cam timing up as per factory Yamaha specs using the correct timing marks, the exhaust valves are hitting the piston. Piston is in the correct direction,valve lash is good, flywheel key is not sheared so any other ideas? I have done tons od 03-09 yama 450's but this is the first 2010-2013 yama 450 I have done.

[grayracer513]

The timing marks on the '10 are NOT at TDC.  Go by the marks, not the piston position.

[noslo98]

I am going by the marks and the exhaust valves hit the piston.

[grayracer513]

Unless you have the exhaust cam in the front of the engine, I can't think of anything.

[noslo98]

No it's in the correct position. I'm kinda wondering if it's a stretched timing chain as well as possibly a timing gear that's rotated on cam. The exhaust cam is super tight, you can't rotate by hand it's so tight. You should be able to rotate the cam until lift by hand.

[sillageman]

I did hear of one 2010 that had the gear move on a cam. thats a really long way for a cam chain to stretch. But it should get replaced anyway.  Id try another set in it If your near san francisco I have a spare set u could borrow.

[noslo98]

Thanks for the offer. I ended up buying a new exhaust cam and timing chain and all is good now. I compared the two before installing, the sprocket had spun about 6 teeth. That would explain why it seemed soo far off.. Lol the bike fired right up so all is good now.