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Valve shims on a 82 gs550mz

  • Thread starter Thread starter zacheriaj
  • Start date Start date
i think i have to find the shim club and see if anyone will trade me. first i gotta find out what size i have in mine. why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?
 
zacheriaj said:
i think i have to find the shim club ...
Click to expand...
Look just a couple of posts above this one for Ghostgs1. In his sig line, you will find a link to the shim club.


zacheriaj said:
... why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?
Click to expand...
They are thick so that they are easy to handle, but they come in different thicknesses. By changing to a shim of a different thickness, you can adjust the clearance between the cam and the shim. The clearance that is specified is there because of the expansion rates of the materials in the head and valves. When they get to operating temperature, there needs to be enough clearance to do the job. Only the engineers that designed the engine know what the operating clearances are, and they don't really matter. What matters is that if we set the clearance to 0.03-0.08mm when the engine is cold, it will be proper when the engine is hot.

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zacheriaj said:
why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?
Click to expand...

The gap which is supposed to be there is very narrow. The spec for your bike is going to be 0.03-0.08mm. At minimum gap - still within spec, mind you - that's thinner than the foil-like 0.0015" thinnest feeler that you can find in most gauge sets. It's been noted several times that the gap tends to tighten with wear. When you stop to think about it, if your valve is closed, what wear points exist in the valve assembly (open you might see the effects cam lobe wear, if you had some method for measuring the "open-ness" of your valves)? The part of the cam you're measuring against should not be in contact with anything, and thus should never wear. The only parts to wear are the valve faces and valve seats to tighten the gap, and the hardened shims to loosen it. The shim is winning the wear-resistance battle there.

Thinking about it more deeply, the camshaft journals can also wear. With the shafts under downward tension from the chain, that would tend to tighten the gap also.

Nothing is wrong - that's just how it works on this motor.
 
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