How thin can a SHIM be?

[Guest]

Another question that came up while shimming the valves. Suzuki lists the thinest shim at 2.15. I am thinking one of mine will need to go down to 1.95. I see that in the list of available stock at the Shim club, there is one 1.65. So how thin can we safely go, before looking for other reasons that made this happen. What could be the consequences of a shim too thin? Y see that the 2.00 is already below the seat hight, but the cam is safely away from it.

[salty_monk]

I would think it would point to serious valve seat recession or some other kind of problem.
Did you do a compression test? What shim have you pulled out of there? It's rare to need one that is a lot different from what you pulled out as it would be burning the valve or holding it open....

[Nessism]

The lip on the edge of the valve bucket will hit the cam if the shims are much thinner than the 2.15 mm. Sounds like it’s time to pull the head down.

[bwringer]

The lip on the edge of the valve bucket will hit the cam if the shims are much thinner than the 2.15 mm. Sounds like it’s time to pull the head down.

Agreed -- something else is Bad Wrong.

[salty_monk]

0.2mm difference is about the thickness of a sheet of paper.... If you are in a hard place & can get a shim at 1.95 I would put one in & then turn the engine slowly by hand to check for interference.
You might be able to get a season or two out of it that way... shame to pull a head at the start of the riding season....

I'm just telling you what I would probably do - make your own call if you want to take the chance.

[Richsuz]

So close to my trip, I will risk it. Going to the States in a three weeks, so I need to Test ride and break in the new rings. Will go over the valves in Sept.

[SqDancerLynn1]

Has the bike ever had the valves ground?? With poor spring height? Definitely needs a compression test, could be the valve stem stretching due to fatigue. You need to take the head off and check it..

[Steve]

0.2mm difference is about the thickness of a sheet of paper....

... only if you are using very thick paper.

Not that it really matters, but most paper that is classified as "20-pound" paper is 0.003" thick.
That is co-incidentally the same as the maximum clearance allowed on the GS valves (for shimmed engines), and that is 0.08mm.
0.2mm would be about 2 1/2 pieces of paper.

.

[salty_monk]

Ok call me a liar... about 2 sheets of copy paper (90 GSM in my world...)

http://www.paper-paper.com/weight.html