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Grinding Shims

  • Thread starter Thread starter amontyg
  • Start date Start date
A

amontyg

Guest
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.
 
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.
 
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
 
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.
 
I installed the shim with the ground side down, and the factory edge up toward the cam.
 
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 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
 
Nessism said:
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.
Click to expand...

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

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.
shrug2.gif


.
 
amontyg said:
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.
Click to expand...

That's what my mechanic does.
 
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.
 
amontyg said:
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.
Click to expand...

Mercaholic said:
That's what my mechanic does.
Click to expand...
Another note to self: don't go to Mercaholic's mechanic. :o

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

.
Click to expand...

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).
 
Steve said:
Another note to self: don't go to Mercaholic's mechanic. :o

.
Click to expand...

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.
 
Mercaholic said:
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.
Click to expand...

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.
 
Lots of difference between the precision of a surface grinder and a dremel tool. I know what my precision level is (or isn't) with a hand tool such as the dremel mentioned. It's your bike and your choice.
 
Dogma said:
I'd do a thing like that as a temporary fix to get home (not that I've adjusted shims on the road).
Click to expand...
I have, sort of. :o

OK, it wasn't on the side of the road, but I did do an adjustment in the hotel parking lot a couple of months ago. :D

Mercaholic said:
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.
Click to expand...
Still has that level of UNcertainty that I would rather not choose to accept. :rolleyes:

.
 
old_chopper said:
Lots of difference between the precision of a surface grinder and a dremel tool. I know what my precision level is (or isn't) with a hand tool such as the dremel mentioned. It's your bike and your choice.
Click to expand...

I agree with this. The only way I'd use a hand ground shim is if it measured flat using a micrometer, not a caliper, and not just eyeballing it either.
 
Thank you everyone for your comments, I have been persuaded to just get a new shim at the correct size.

I have had the shim in for three days now, and it seems to work fine, but just to be safe I think I'll park it and wait for the correctly sized shim to come.
 
....and thank you all for confirming that I don't want to use some home ground shims I inherited that have a 3-4000th in. variance in them. I'll donate those to the Shim Club, since Ray has a precision grinder. I do have two home ground shims that measure perfectly uniform (at least as uniform as a factory shim anyway) with a micrometer, so I'm not worried about them.
 
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