shimming valves - what did i do wrong?

i checked my valve clearances and found that my left intake valve was perfect (.06) and my right one was off a hair (.04).

i have a 165 in the left side and a 170 in the right side.

i changed the 170 to a 165 in the right intake and put the valve assembly back together.

now BOTH sides are even tighter than they were before.

i appear to be at top dead center judging from the kick start side marker and the cam chain sprocket and marker on the cam assembly and the rocker arm on the exhaust valves is loose.

what did i do wrong? did i mess up the timing?

this isnt my first shim job but my first solo.

my bike is an 08 crf450r.

Sounds like when you put your cam back it it wasn't in the right location, needes to be lined up at top dead center when you installed it, or you might have over tightened the bolts 11ftlbs i believe, or when you put the cam tower on it didn't go on straight ( did you tighten the bolts evenly.

how much tighter? Double check timing..sometimes it will look like its in time, but when slack is taken out of cam chain, its actually a tooth off..and like previously posted..easy on the cam tower bolts

Take out the plug on the left side of the engine the flywheel side and there are two marks on the flywheel the one to the right is top dead center put that on the mark in the theads and check the cam again

after i put the new shims in i had a hell of a time getting the cam sprocket back on. i didnt make sure the engine was at TDC when i removed the last sprocket bolt and pulled it off.

i torqued the assembly bolts to 10 lbs according to my wrench.

ok. i will check the timing.

thanks for the suggestions.

ill let you know what happens.

i had a hell of a time getting the cam sprocket back on.

did you release the pressure on the cam chain?

Sounds like the shims are not seated correctly, they most likely came unseated when you put the cam on if the buckets were on the valve first then you tried to put the cam housing on.

did you release the pressure on the cam chain?

i used a small screwdriver to hold the tensioner and didnt realized it had let go. so not at first but i corrected it.

Sounds like the shims are not seated correctly, they most likely came unseated when you put the cam on if the buckets were on the valve first then you tried to put the cam housing on.

i double checked this today at lunch. i pulled the cam assembly off remeasured the shims and carefully put it back together making sure the shims were positioned properly. this was one of my first thoughts when i had problems.

so i have the right side timing marks lined up, the cam sprocket indicator and the arrow on the tower are in line but i dont have the flywheel and its marker on the threads in line. in fact i dont even see a timing mark on the flywheel.

the flywheel is a 15oz trail tech.

no timing marks on the trail tech flywheel.

i loosed the cam assembly bolts all the way and only just hand tightened them back down to get a measurement of the valve clearance. still tight.

the right side timing marks and the marks on the cam sprocket and tower are also spot on. i removed the cam chain tensioner. the exhaust rocker arm is free.

i think the only explanation left is that i messed up measuring the clearance the first time.

Edited by knucklehead
i did check tdc.

Are you sure it was a 165 and not a 185?

That would suck!!

Take the cam chain off and turn the cam around a couple times to seat everything and remeasure.

Even if you over torqued the cam tower it shouldn't mess with the lash number. The cam chain tensioner can mess with you a tiny bit on the left side. It takes up any slack in the big cam bearing and you loose the lash in that side. Ya really oughta check the lash with the chain on and tensioner loose, because that's the way it runs, ya know?

Are you sure it was a 165 and not a 185?

That would suck!!

Take the cam chain off and turn the cam around a couple times to seat everything and remeasure.

Even if you over torqued the cam tower it shouldn't mess with the lash number. The cam chain tensioner can mess with you a tiny bit on the left side. It takes up any slack in the big cam bearing and you loose the lash in that side. Ya really oughta check the lash with the chain on and tensio/ner loose, because that's the way it runs, ya know?

i measured the shims with the calipers. they are correct.

by taking the cam chain off you mean removing the sprocket and chain and setting it aside while i rotate the crankshaft on the right side of the bike. do i need to loosen the tension on the cam chain? if i dont the chain wants to pull the chain and sprocket down towards the bottom of the engine.

i have been measuring with cam chain on, bolts on hand tight, and no tool in can chain tensioner.

i am about to test some 160's in each intake and see what happens.

You will close the clearances by over torquing the cam tower if you don't use a good torque wrench.

i measured the shims with the calipers. they are correct.

by taking the cam chain off you mean removing the sprocket and chain and setting it aside while i rotate the crankshaft on the right side of the bike. do i need to loosen the tension on the cam chain? if i dont the chain wants to pull the chain and sprocket down towards the bottom of the engine.

i have been measuring with cam chain on, bolts on hand tight, and no tool in can chain tensioner.

i am about to test some 160's in each intake and see what happens.

you can measure the valves with or without the chain on ..with the chain off it makes it easter to get the feeler gauge in by spining the cam back and forth a little

You will close the clearances by over torquing the cam tower if you don't use a good torque wrench.

I dont see that happing more likey stripped threads

You need to measure the clearances with the cam in a running style state. In other words, the tower needs to be torqued and the chain on the gear and the tensioner released so the chain is pulling on the cam. That will take up any clearance in the big end bearing of the cam and the clearances there will be ever so slightly less. But they still need to be about .005" on the intake on the left side with everything set.

You can probably figure out your fudge number by measuring with the chain on, then with it off and see the difference and then you can save some time by guesstimating the shim thickness needed to get back where you need to be.

Remember, the shim sizes only change about .002" from a 170 to a 165 etc.

I still say spin the engine around a dozen or so times to seat everything. The 165 should have put you right at .06 on that right side. And you didn't change anything on the left so I say its just a matter of getting things seated.

I know its a little late now but where those original clearences even bad to start with?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now