Shim Question

working on the putting the 750 head back together thats going on my 650-810 project.

I have all the valve clearances pretty close. found a guy down the road that had a bunch of the 13mm shims (under bucket).

the clymer manual isn't too in depth with the whole process. im shooting for .15 and ive got them all to either .12 or .17 (some at .15).

my question is which is better, too much clearance (.17) or too little (.12)? my initial thoughts were too much (.17). since they come in incriments or .05 im not suer which way to go. What do you all think?

thank you.

I'd say too much. That way when it breaks in you have more leeway. I'd imagine it'll decrease a fair amount over the first couple of thousand km.

To much clearance, the shim can jump out. To little clearance, you burn a valve.

i just realize that i assumed that the 750 and 650 heads would have the same valve clearances. am i wrong?

could someone please tell me what the 750 FSM says the valve clearances should be? is there a range or just a #, all i can find in my 650clymer is .15mm.......i dont see a range.... whats the 750manual say?

thank you

kzz1p wrote:

To much clearance, the shim can jump out. To little clearance, you burn a valve.

Do under-bucket shims have a problem with jumping out with too much clearance?

They are all the same. Generally .10-.15mm is what you are trying to get.

Can't help with the 650 vs. 750 clearance specs as I have no info on the 750s (650 spec. is .15 mm as you say), but I'm sure someone else can give you the right numbers.

However, determining shim size you should always round the .05 mm increments up - valve clearance on these engines can only diminish over time so loose is better than tight = .17 mm is better than .12 mm (given the spec is .15 mm).

If it has a fresh valve job, it will tighten up slightly.

Jay