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Need new valve?

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While helping my buddy check his clearances we found that his left intake is zeroed out.

We tried a shim calculator that we found online and we're not sure of the results (current - 1.62, calculator called for a 1.614). Thinking about it now, that is probably right, as I didn't realize there is a .006 difference between the two numbers.

Anyways, we called a local shop (very reputable, buddy has a small sponsorship). They said that since the valve is zeroed out that it needs to be replaced. When asked if we could shim it they said "yes, but it will need to be re-shimmed every hour or so". My buddy wanted a second opinion and asked me to post on TT for him.

I'm sure the "right" thing to do is replace the single intake, but can he re-shim this time and keep an eye on it? The right intake was in spec, and my buddy would like to shim the left until both valves need to be replaced or until the left will not stay put. Opinions?

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when you are "zeroed out" you are not able to calculate a shim size.

you need a clearance value to determine that.

how did you determine your spec?

if this is the first time to reshim, let alone check, you could probaly do it a few times, but it will move pretty fast.

faster than waiting for the other to close up for sure.

the left side closes first.

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Both of my CRFs had the right valve tighten up first. Left side, right side......it varies.

Anyway, yes you can shim the valve back to spec. You'll get more than one hour of riding time on it before you have to shim it again. But, you will have to shim it again. Once they're zero'd out you're screwed. When my intakes tightened up, I was able to get a ride or two out of them before I had to shim them again.

To ge the correct shim in there, remove the shim and right off the bat subtract .006" from that. Figure which shim you need, and install that one so you can at least get a feeler gauge between the cam and lifter. Then you will be able to get a measurement and go buy the shim which will get you back to .006" of clearance.

My advice would be to replace both intake valves with stainless steel intake valves and springs as soon as possible.

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