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Polishing valve shims to the right thickness

  • Thread starter Thread starter mljbone
  • Start date Start date
M

mljbone

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Hi, I'm about to check valve gaps on my '81 GS650L. I've cleaned and put new O-rings in carbs and boots. Also I've sealed air box. My question is if my gaps are tight, is it a bad idea to polish down shims and mic to right thickness? I got her 3 weeks ago, and couldn't get it start without a squetr of quick start. I think it would be easy enough to use wet/dry sandpaper (1200) to get them within specs. Thoughts?
 
Everything i have read about it says it is very difficult to get a uniform thickness.
This may cause the shim to move inside the bucket.
 
They cost like $5 a piece and you can re-sell the old ones on ebay and get half your money back. Just get new ones already.
 
We also have a "shim club" here on GSR. Contact member Ghostgs1 for details.

I think it's basically free, except for the postage, although donations are never refused.

.
 
"I think it would be easy enough to use wet/dry sandpaper (1200) to get them within specs. Thoughts?"

Maybe a few days-are you really bored? No, then just join shim club. Don't worry there will be lots of fun other stuff to keep you busy. Sounds like you got carb removal and cleaning to do, otherwise this critter will never run right.
 
Best way is to surface grind them with coolant flowing so they are perfectly flat..coolant so they dont heat up while grinding. Take very very thin sweeps so you dont suck the shims off the table. Very hard to block shims in unless you have some thinner steel around that you can use to block with.
 
Just let Ray at the shim club do it. He has the proper machines all set up and a metric ton of shims ready to go.
 
I can't believe that grinding the stock shims is even being debated. I don't know if these are surface hardened or the same harness throughout but I wouldn't take the risk. Just not worth it to save a couple bucks.

Just pick up the correct size replacement shims. In most cases you can shuffle them around and you'll only need to purchase a couple.
 
Hardened all the way thru and they did it all the time back in the day. If I had a surface grinder I would do my own too. Bet you send Ray a message and he has ground them too.
 
I've ground a couple of mine, but as with everything, it's knowing how and what to do. Not every solution is on a shelf.
 
JTGS850GL said:
I can't believe that grinding the stock shims is even being debated. I don't know if these are surface hardened or the same harness throughout but I wouldn't take the risk. Just not worth it to save a couple bucks.

Just pick up the correct size replacement shims. In most cases you can shuffle them around and you'll only need to purchase a couple.
Click to expand...

They are hardened all the way through. Haven't had any trouble with Ray's shims, nor have I heard of anyone having trouble. He has a lot of each size, he would probably send unground ones in whatever size you need if you asked him politely. He sends them out, once you swap them you send him your old ones, everybody is happy. Except the folks who sell shims for $10 apiece.
 
I had my 450's shims taken down. There was a shop that had second hand shims and charged a fortune for them, plus wanted the old ones.

my (then) neighbour has an engine rebuilding shop and they often get requests to grind down shims.

kept record of them using Steve's spreadsheet.
 
I also have reduced thickness using wet and dry+ some wd40, its an ok method, the way to get round the uniform thickness is to rub them in a figure 8 and rotate 90 degrees every 10 or so figure 8s'. Takes a long time and really ok if its you got no choice.
 
I actually re cut shims on a lathe, makes me think they were handed throughout, need some special tooling tho. If it were me get me from the shim club...
 
JTGS850GL said:
I can't believe that grinding the stock shims is even being debated. I don't know if these are surface hardened or the same harness throughout but I wouldn't take the risk. Just not worth it to save a couple bucks.

Just pick up the correct size replacement shims. In most cases you can shuffle them around and you'll only need to purchase a couple.
Click to expand...
Agreed, grinding shims is a fool's errand unless done professionally. If your time is worth anything just buy new ones
 
chuck hahn said:
Hardened all the way thru and they did it all the time back in the day. If I had a surface grinder I would do my own too. Bet you send Ray a message and he has ground them too.
Click to expand...
OK then. Now I know it can be done and by who. I stand corrected. I just wouldn't trust hand sanding them to get them even.
 
JTGS850GL said:
OK then. Now I know it can be done and by who. I stand corrected. I just wouldn't trust hand sanding them to get them even.
Click to expand...

Doing it by hand would be a last resort for me, but uneven and too thin would be better for the engine than too thick. Too thick burns valves.
 
tkent02 said:
Doing it by hand would be a last resort for me, but uneven and too thin would be better for the engine than too thick. Too thick burns valves.
Click to expand...

Just be careful that you don't go too thin and risk having one shatter or having the cam lobe hit the bucket.
 
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