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Shim selection suggestion

JTGS850GL

JTGS850GL

Forum Sage
Past Site Supporter
OK, I've started replacing the shims on my GS850. The first three went pretty much as expected with the final clearance falling into the .05 to .08mm range. The next one is a little bit out though. It started at somewhere between .03 and .04mm with a 2.60mm shim. I replaced it with a 2.55 and now the gap seems to be around .10mm. I know that most say to go on the large side but should I stay with the original shim, jump to the larger shim or try to locate a 2.55+ shim?

Edit: Just measured it using another gauge set and it comes in at exactly .004" or .102mm.
 
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Yep -- it'll be fine.

Many of us routinely run clearances up to .10mm or .11mm.

Slightly larger clearances are perfectly safe. Tight clearances can cause damage.

And standard GS valve clearances are very small compared to most -- you won't even notice any extra noise.

The Kawasaki KLR650, for example, uses a nearly identical shim-over-bucket system, and its clearances are 0.10mm – 0.20mm on the intakes and 0.15mm – 0.25mm on the exhaust valves.
 
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bwringer said:
Yep -- it'll be fine.

Many of us routinely run clearances up to .010mm or .011mm.
Click to expand...

I'm assuming that you meant .10mm or .11mm.

Thanks guys!!! Just wanting to make sure before I get too far along. The carbs are out for a good cleaning by cheff1366 and should be back in a week or so. Figured by then I'll have all the other incidentals completed.

Still have a slow responding tach to clean up, a light lens that popped out inside the speedo to glue back in, a kickstand switch replaced and a couple illumination bulbs replaced in the gauges.

Already done: Replaced the oil and filter, diagnosed & replaced the bad R/R, fixed & sealed up the screwed up air box/filter, replaced the intake O-rings and damaged intake boots, reconnected the broken wires to the fuel gauge, glued loose handled bar grips and replaced the mangled tach & tach cable from when the PO dropped the bike.:mad:

Hope to be able to ride her soon.:D
 
All the new shims are installed and, with a little shifting things around, I was able to get everything within .05 and .09mm. Everything all buttoned up and ready for the carbs to get home next week. Decided to replace the plugs with new NGK B8ES gapped to .030".

In the mean time I was able to disassemble the speed-O to fix the kickstand lens that fell out and the crack in the background plate. I used the de-crimp method on the lens to open it up and replaced the lens and outer bezel from a tachometer that was blown inside but had a perfect lens and bezel. Looks good now. Replaced all the bulbs with new 158 bulbs while I was in there.

Slowly she's coming together.:D
 
One odd thing I've found is that if you use a micrometer on your shims, you'll find that the older shims (made in the 70s and 80s) are somewhat variable, often .01 or even .02mm each way.

And then, of course, you sometimes find the mystical "X" or "fat" shims -- they're marked with an X after the number (2.70x) and are usually .02 to .03mm thicker than the printed measurement. These were only used at the factory.

Newer shims, such as those from a newer GS500 or new aftermarket shims, are always dead-on.
 
Yep, found quite a few "X" shims. Hard to read at first so I ordered new shims based on the none X sizes. Still worked out in the long run. I'm guessing that it may very well be possible that all the shims on my bike were the factory originals since all shims had the same style of markings and most were X sizes.
 
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