Valve clearance

Hi Guys! Checked valve clearance over the weekend. Intake within specs. at .011'', exhaust on low side at .005'' ( range is .006'' to .008'' ) This motor has 2 years plus riding. How soon again should I ckeck them? Didn't bother re-shimming on account of .001''. '99 YZ420 Thanks.

That's hard to say...but, I would probably check it again after about 15 more hours of run time. They may not change by any discernable amount the next time you gauge them. Now that the exhaust valve(s) show a slight "tight" tolerance, I'm sure you don't want to burn a valve or do other damage by a valve slamming into the seat repeatedly.

I would say---shim it!!! Like Boit said, you do NOT want the valve damage that may be caused by the .001 clearance difference. As I am sure you know, the time and cost to shim it within specs is sustantially less than rebuilding the head and/or top end.

O.K. , will order the shims today. Thanks for your input. Didn't think a few thou would matter but better safe than sorry. Thank-you for your time!

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