Grinding Shims

[amontyg]

I just got a new batch of shims for my latest valve adjustment and realized that I ordered one at the wrong size. I needed a 2.6 and ordered a 2.65. I really didn't want to get back into the bike again, and didn't want to wait another week, so I decided to try grinding down the shim.

I first put the shim on my belt sander turned upside down, but noticed that the edges were getting ground down faster than the middle. So I broke out my dremel tool and ground down the middle until it read 2.6 all over. I then rubbed it on some sandpaper until it was smooth again, and installed it in the bike.

my bike seems to run fine; I guess my question is whether or not this is in someway going to cause a problem. I'm looking for some reassurance I suppose.

[old_chopper]

Not a great way of doing that. It could be sitting on an angle and start wearing the cam in a hurry. Best to either buy the right shim or have a shop surface grind it flat for you.

[BassCliff]

Hi,

As long as you have the proper clearance and the smooth side is up, next to the cam lobe, you're good to go.


Thank you for your indulgence,

BassCliff

[850GT_Rider]

I'm not sure if the shims are the same hardness throughout. They MAY have a hardened case (for wear resistance) with a softer core (for strength).

Just speculation tho. Never sectioned one to look at microstructure.

[amontyg]

I installed the shim with the ground side down, and the factory edge up toward the cam.

[Nessism]

I think you should be fine but I'd use a micrometer to measure the thickness. As long as it's flat, and the ground side goes against the bucket, I think it will work fine.

[Ghostgs1]

I think you are fine. These shims are made of a through hardening alloy steel. Like wisgolfer suggests, if you look at a cross section of a broken shim, the grain structure is the same all the way through it. This is why they are quite brittle. Ray

[1980GS1000E]

I think you should be fine but I'd use a micrometer to measure the thickness. As long as it's flat, and the ground side goes against the bucket, I think it will work fine.

I had to grind one of my shims, well, I lapped it actually with a plate and progressively finer grit paper, and put the factory side against the bucket. My thinking was the clearance is between the shim and cam so I wanted the fitment between the bucket and shim to be as tight as possible to take advantage of the oil's film strength and suction, hopefully avoiding a possible spit.

[Steve]

Note to self: Don't buy anything that amontyg has worked on.

Sorry, dude, there's just too much opportunity for problems if you don't use precision equipment for that kind of modification.
Ghostgs1 has (had?) access to proper equipment to do that, and started the "shim club" in the process.

As much as I enjoy riding any of my bikes, I don't think that using a shim of basically unknown qulaity (and thickness)
will take priority over waiting about three days for a new shim from the shim club or Z1 Enterprises.

.

[Mercaholic]

I just got a new batch of shims for my latest valve adjustment and realized that I ordered one at the wrong size. I needed a 2.6 and ordered a 2.65. I really didn't want to get back into the bike again, and didn't want to wait another week, so I decided to try grinding down the shim.

I first put the shim on my belt sander turned upside down, but noticed that the edges were getting ground down faster than the middle. So I broke out my dremel tool and ground down the middle until it read 2.6 all over. I then rubbed it on some sandpaper until it was smooth again, and installed it in the bike.

my bike seems to run fine; I guess my question is whether or not this is in someway going to cause a problem. I'm looking for some reassurance I suppose.

That's what my mechanic does.

[Counter]

You probably ground down the side that was not marked. If so, the marked side will be up and meeting the cam lobes. If that is so, you might want to mark the down side with the thickness as the thickness markings on top could be worn down over time.

[Steve]

I just got a new batch of shims for my latest valve adjustment and realized that I ordered one at the wrong size. I needed a 2.6 and ordered a 2.65. I really didn't want to get back into the bike again, and didn't want to wait another week, so I decided to try grinding down the shim.

I first put the shim on my belt sander turned upside down, but noticed that the edges were getting ground down faster than the middle. So I broke out my dremel tool and ground down the middle until it read 2.6 all over. I then rubbed it on some sandpaper until it was smooth again, and installed it in the bike.

my bike seems to run fine; I guess my question is whether or not this is in someway going to cause a problem. I'm looking for some reassurance I suppose.

That's what my mechanic does.

Another note to self: don't go to Mercaholic's mechanic.

.

[Dogma]

Another note to self: don't go to Mercaholic's mechanic.

.

This all does sound like a lot of work around for a shim that should only take $10 shipped from Z1, a couple days wait, and a few more minutes installing. Instead, you have a component at the heart of the valve train surrounded by questions of whether it's all right. It may be OK, but it's not a methodology for mechanical reliability. I'd do a thing like that as a temporary fix to get home (not that I've adjusted shims on the road).

[Mercaholic]

Another note to self: don't go to Mercaholic's mechanic.

.

Clarification: Instead of ordering new shims, my mechanic has a machinist that will correctly work the existing ones to the spec needed for re-installation.

[hampshirehog]

Clarification: Instead of ordering new shims, my mechanic has a machinist that will correctly work the existing ones to the spec needed for re-installation.

That's ok. I've got a mate who has a shim grinding machine in his shop. He made some shims a bit thinner for a Lancia I rebuilt a few years ago though he's never needed to do any for my bikes.