Limit on Valve Adjustment-WR426

Anyone know how much shimming adjustment on the valves can be done before valve replacement is needed? Now much I'm guessing with the thin Ti valve face coating.

thanks, harold

Anyone know how much shimming adjustment on the valves can be done before valve replacement is needed? Now much I'm guessing with the thin Ti valve face coating.

thanks, harold

here is the link to the motherload of links.

http://www.thumpertalk.com/forum/showthread.php?t=447989

Read through those and it should answer your questions.

I know for the 250 you can get after market shim kits that range from 1.20mm to 3.5 mm in increments of 0.05 mm

Typically, after the 2nd re-shimming, you need to do the valves. You do not go by running out of thin enough shims, you do it by the number of times.

When a valve job is done by a competent shop, the shims needed will be mid range, affording more than enough adjustment possibilities.

+1

If you need to shim it and find soon after you need to shim again then it's time for new valves. These bikes rarely need much in the way of valve adjustment so if you suddenly find it going out of spec often it's a sure sign you've punched through the hard coating.

Thanks all. My center intake closed up completly. I dropped 0.11 mm off the shim size and it's still a little tight but I've got cold start compression again. The other intakes are fine. Never been shimmed.

Guess I'd better, sigh, order a valve and a head gasket. Do the seats in the WR hold up pretty well or do they typically need cleaning up a little before installing new valves?

harold

Depends. Sometimes they are fine, sometimes not. If you are just a trail plonker like most of us, a scotchbrite scrubbing and careful inspection with a maginifying lens will tell you if the seat is reasonable. A racer would get it cut on a Serdi machine without thought. Do new valve seals while you have the head off.

At 67, I am mostly a plonker. I have a 20x optical micrometer, so I'll do as you suggest.

Why replace the seals? Are they a weak point on the WR? I have a 94 KLX with at least 50k miles and probably more that has never had the seals replaced during a dozen or more intake valve replacements with no oil loss between changes.

harold

Valve seals are cheap. They do leak from time to time. You will of gone to the trouble of taking the head all apart, why not change the seals.

Sort of like taking a shower and not bothering to wash your big toe. You got all wet and soapy, might as well finish the job.

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