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thumpyz

04 yz450 valve questions

2 posts in this topic

Well, right now my steed is down for other reasons, so i am doing some preventative maintenance. I am checking the valves(my first time, on my first 4 stroke) and i just have a few questions. When finding tdc, my punch marks line up perfectly,but the I mark is about 1/8th of an inch forward of the mark in the case, According to the manual this is not right. Does this mean my timing is off? Also one intake valve is "tight". It is measuring at .076mm. Does this kind of wear seem normal? Any and all help is greatly appreciated.:thumbsup:

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Line the I (not the "H" that is just to the left of it) up first, then check your cams. The cams turn at half speed, so the crank moves quite a ways without moving the cams that much.

When you look at where the cams are with the crank lined up, and they don't line up perfectly (and they probably won't), ask yourself what moving them one tooth would make them look like.

Your tight valve means one of two things:

> The valve has moved into the seat by a very small amount, and if you adjust it, everything will be fine.

> The coating on the valve has worn through, and if you adjust it, it will be tight again within 6 hours.

Shim the valve and check back after the next ride or two. If it hasn't moved, your OK, if it's already tighter, then it's time for a valve job.

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