Valve shims

[amontyg]

I am currently working on doing the valves for my 82 gs550l for the first time. The clearances are very tight to say the least. Anyway, on a lot of the shims marked with an x would be the ideal size but i don't really see those for sale in any of the online fiches. Can you buy these or do you have to just come across them?

[TheCafeKid]

I am currently working on doing the valves for my 82 gs550l for the first time. The clearances are very tight to say the least. Anyway, on a lot of the shims marked with an x would be the ideal size but i don't really see those for sale in any of the online fiches. Can you buy these or do you have to just come across them?

Generally, you have to happen across them. Steve and I have been rather fortunate in that the last 3 or 4 bikes that we've done valve adjustments to had a fair share of the coveted "X" shims in them, so consequently, have built up a bit of a stash. But, use the shim closest to what you need. Even if its a little loose (say, .09 to .10 clearance) it will only get tighter with wear, so in pretty short order it will be within spec. That loose isnt a real worry on a normal street bike, any looser than that however, and you might run the risk of floating a shim out of the bucket at high RPMs, and that would be instant death.

[Headphase]

whats the coveted (x) then, cos I was doing the shims on a 650 last night and one had the markings 270(x), it looked blue compared to the other ones as though it was made of a different metal or something.

[TheCafeKid]

whats the coveted (x) then, cos I was doing the shims on a 650 last night and one had the markings 270(x), it looked blue compared to the other ones as though it was made of a different metal or something.

Its not a 2.70 or a 2.75. Its probably a 2.73 or 2.72 or something like that. They are coveted by the tuner/racer types because it allows them to get thier valve clearances exact all the way across the board. This way the valves all open the same amount across the cylinders. Other than that, Im not sure what the real advantage is.

[Headphase]

awesome, I will treasure it always then

I'll measure it tomorrow, see what it really is, just out of nosiness.

Thanks

[Suzuki_Don]

They are what we call "FAT" shims and are usually 0.02mm or 0.03mm over the size stated on the shim. Never take for granted the size stamped on the shim either. They could have been ground or rubbed down to a different size to suit a certain application. Always measure with a vernier caliper for a true reading.

[chef1366]

Half sizes.............

[rudy]

They are what we call "FAT" shims and are usually 0.02mm or 0.03mm over the size stated on the shim. Never take for granted the size stamped on the shim either. They could have been ground or rubbed down to a different size to suit a certain application. Always measure with a vernier caliper for a true reading.

One of my roommates told me once that a vernier isn't very accurate for measuring something that small. That kinda struck me as strange, as I was actually measuring my shims when he said it. He's a machinist, so I took his word for it, but continued using my vernier and trusting it. Any thoughts on this? Also, what would be more accurate?

[chef1366]

One of my roommates told me once that a vernier isn't very accurate for measuring something that small. That kinda struck me as strange, as I was actually measuring my shims when he said it. He's a machinist, so I took his word for it, but continued using my vernier and trusting it. Any thoughts on this? Also, what would be more accurate?

That small????

[rapidray]

Tell your roommate to go back to what he's doing & keep using your vernier! Ray.

[Suzuki_Don]

I've actually found that using a micrometer over different areas of the shim gives slightly differing readings and using the vernier gives one averaged reading which suffices for my applications.

As Bill says what about "THAT SMALL". I use a vernier on my feeler gauges before doing jobs like measuring ring side clearance and the vernier measues exactly what the reading on the feeler gauge is. Is 0.003" small.

[JJ]

>Tell your roommate to go back to what he's doing & keep using your vernier! >Ray.


I have worked as a journeyman machinist in the aerospace industry.... as a CNC programmer... and have a BSME from GA Tech... As a general rule, I would NEVER trust more than a semi-close tolerance (+/- .005") measurement to calipers.

I will qualify that by saying that a seasoned machinist could probably be accurate within +/- .002". The general layman could probably not measure repeatedly any closer than +/- .005" with a pair of calipers.

[rudy]

>Tell your roommate to go back to what he's doing & keep using your vernier! >Ray.


I have worked as a journeyman machinist in the aerospace industry.... as a CNC programmer... and have a BSME from GA Tech... As a general rule, I would NEVER trust more than a semi-close tolerance (+/- .005") measurement to calipers.

I will qualify that by saying that a seasoned machinist could probably be accurate within +/- .002". The general layman could probably not measure repeatedly any closer than +/- .005" with a pair of calipers.

While I have to agree with you for most applications like measuring parts and so on, would it really matter that much with valve shims? They fit pretty dang well in the jaws, and I always measure stuff two or three times to make sure...... then usually forget what the measurement was a second later, and have to do it again.

As with all moving parts, there has to be some kind of lash and tolerances for movement in those gears and the stuff that moves the dial on the vernier, no matter how well it's made.

[TheCafeKid]

While I have to agree with you for most applications like measuring parts and so on, would it really matter that much with valve shims? They fit pretty dang well in the jaws, and I always measure stuff two or three times to make sure...... then usually forget what the measurement was a second later, and have to do it again.

As with all moving parts, there has to be some kind of lash and tolerances for movement in those gears and the stuff that moves the dial on the vernier, no matter how well it's made.

I have to say your roommie is being a bit anal in this situation. Im no machinist, and he may be right, but this is why there is a range given. .03 to .08mm. If you slap a shim in there expecting a .08 clearance and its .09, oh well. If its .07, oh well. If it was .03 (or most of the time for me, even .04) its coming out of there, and the next shim is going to take it where it takes it. I have read and heard tale of even old school race bike builders running as loose as .15mm and never having problems (not gonna try it, but just saying)

Now, I will say that sometimes, when I measure a shim as I was taught, I rotate it, getting readings from a few different degrees of the shim, now and then I will get, say 2.70 most of the way around it and in one spot i get 2.72. Oh well....in she goes...

[chef1366]

I would think that .15 would start compromising the lift on the cam.