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05 YZ450f won't start!

3 posts in this topic

I bought this used stud of a machine used about 10 months ago. Really powerful bike, has an aftermarket intake, exhaust , aluminum head, and "some work on the carb".

It ran fine for 7 months, but it started having some problems idling. Long story short, it got to the point where it was hard to kick start.

I took the carb off and apart, cleaned it thoroughly, put it back on. Now the bike wouldn't kick at all, but it would pull start behind a quad.

I read up online and thought it might be the valves, sure enough they were out of spec and the timing marks were off on the cams. To fix the timing, I put the bike at TDC and took the cams out, then set them back in where they should be. Put the bike back together, still won't start.

As far as I know the only thing out of place is the valve specs, could this keep the bike from starting??

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I've fixed the timing, re-measured all of the valve clearances.

Exhaust clearance spec is .2-.25 and both valves are sitting between .2-.23

Intake spec is .1-.15 and they are all right above .15 by as much as .03 and .05 mm....

I will make a trip to town tomorrow and try to shim the valves smack in the middle of the specs but as of now, that wouldn't be enough to keep the bike from startin would it?

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