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what is the smallest valve shim you can run?

DimitriT

DimitriT

Forum Sage
Past Site Supporter
This is for the GS550. I had to go with a 2.60x shim recently on two cylinders and it
brought to mind the question: how much further can I go as far as shims before I need to
replace the valve seats?
 
When performing a valve job on a GS engine, it's advised to skim the valve stem a little to move the shim range back to normal. No need to replace valve seats.
 
+1 on Eds statement. Figure out how much would be needed to be taken off each valve stem to get you back to around the 2.75 range. Have your numbers ready and each valve numbered for the machine shop so they take the right amount off each one.

And no, just taking the same amount off each one will not work because of the wear factors to each individual valve and its corresponding seat.
 
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Just a follow up thought...I would do a complete valve job before taking any readings to see what each may need. That way your starting with fresh seats and for sure good valves and remember to check the wear limits on the springs as well.
 
You are in good shape, lots of miles before you ever will need to worry. Some folks have a few shims of less the 2.15mm thickness still running well. Trimming the valve stem would add many more usable miles after a valve job.
 
Very thin shims bring risk. Most drag racers won't use shims much under 2.30mm-2.35mm - high lift cams hammer the shim and can shatter them. That's not really an issue on a mild street bike engine - but still something to consider...
 
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