YZ450 Valve Clearance

I own a 2005 YZ450F and I have about 32 hours running time on it. I just checked the valve clearance and noticed that one of the intake valves had about .076 mm of clearance. The others were about .102mm. The manual calls for .10-.15mm for the intake valves. So, should I adjust the one slightly off intake valve, or is it okay to run the bike the way it is? Thanks, Matt

It's out of spec, and needs to be corrected.

That's what I was afraid you would say. Thanks, Matt

Gray,

What do you think caused this? The first time I had checked the clearance, I noticed the one valve being tighter than the rest. Did the valve settle into the seat a little more than when it left the factory? Thanks for the help, Matt

There could be a number of reasons for it. Probably, the valve seat was not machined quite perfectly enough, and may have had to wear in a bit more than the others. Keeping the valves in spec will make them live longer than if you allow them to run out either tight or loose.

But that valve should not have moved that much so early, IMO. Watch it to see if it keeps moving. If it's just a little glitch in the seat, it will wear in, the wear will go to normal levels, and the clearances will stabilize.

If the seat is way out of square, or the valve is faulty, it will continue to wear faster than the others. You should talk to the service manager at your dealer and let him know what's going on, so that it can be documented.

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