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pwallnuts08

valve clearance question

7 posts in this topic

07 wr 450, im getting kind of tight readings. The intake calls for .10-.15 mm and two of the three seem spot on (.10) but one is tight, .10 will not fit and my gauge doesnt go lower. The exhaust spec is .20-.25 mm and i can only fit .175 in there. It was running GREAT but i had a trans problem to address so i had it all apart. Is that "far off" to be .025 tight? are you worse off to be tight than loose? help!:bonk:

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i just also wanted to mention that i've had the motor apart for over a month now, by any chance do they measure up tight after the initial reinstall? Would they compress after the motor has run?

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The manufacturer must assume that with less clearance, there will be more wear on the cam lobes or rocker's. I don't know anything about the WR, but most modern 4 strokes outside of honda and the occasional KTM are double overhead cam and the cam itself hits the bucket with the shim underneath. So if there was less clearance in that area, then you'd get more wear on the cam lobe itself. I don't think you'll cause any damage with it only a tiny bit off spec. Just remember, when the motor is hot, the clearances are even tighter... :bonk:

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the right way is to shim them to spec ... if its tight .

best not to shim them to spec and forget about it ... check them on a regular basis to make sure there is no movement [ tighter ] if the clearances are decreasing you have valve / seat issues

keep a record of the measurements

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Best place to post a question like this in the WR450 forum. So I moved it.

You will also find if you use the search function, chances are, the question has already been asked several times and excellent answers are already waiting.

See the bottom of this page for examples.

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Yeah, I'd readjust them all to spec. Yamaha is known to run them somewhat snug from the factory, but not me. I set them all to the loose side of the spec (.15 on Intakes, .25 on Exhausts). This way they have quite abit of room before they get too tight. If you run the engine with them on the tight side, they stand a very good chance of being damaged from the heat of the combustion chamber. Valves have to shed there heat by seating on the valve seat a certain amount of time, and this is achieved by the specified valve clearance. Maniac

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i just also wanted to mention that i've had the motor apart for over a month now, by any chance do they measure up tight after the initial reinstall? Would they compress after the motor has run?

If you put the top end together using assembly lube or put plenty of oil in and around the buckets/shims......then the answer to your question is "yes". They will measure tight until you run the motor.

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