All shims are too thick, do I have to order everything thinner than 2.65?

[TheDuke]

So, the title says it all. I'm rebuilding the motor of my '79 750E and had the valves/valve seats recut. Now, all the shims appear to be too thick. The thinnest ones I have are 2.65 and even with that I'm not able to get to the lower end of the range (0.03 mm gap) :|.

In order to know which I need for each valve, do I have to order all the thinner sizes so that I can try them out, figure out which thicknesses I need, and order the appropriate combination of sizes?

Alternatively, does anyone out there have a selection of the thinner ones that I can borrow just to test fit??? Then I will know which 8 to order.

Any advise is much appreciated.

 

[tkent02]

Get one thin shim, swap it around while you measure and figure out the eight you need. Do not rotate the cam with no shim in place in any bucket, it will get damaged.

 

[TheDuke]

Great idea, I will order the 2.15 and give it a shot. In this case then, I'm just adding the gauge thicknesses to that of the shim until it just passes below the cam lobe with a little rubbing and then subtract the 0.03-0.08 clearance to get the shim size I need?

 

[Steve]

That is the basic idea.

Or, you can just measure your clearance, then count how many times you have to subtract .05 before you get into range. Then add that many shim sizes to your 2.15, or whatever you use.

You can also take advantage of the offer in my sig.

.

 

[Guest]

If all your old shims are too thick, even on the intake side makes me wonder if valve stem installed height is too high. Who ever ground the valves should have ground something off the stem to compensate.
It may not be an issue with these engines, but I have seen this sort of thing happen on others when even the thinest available shim will not get clearance.

 

[TheDuke]

If that is the case I will have to take it back to the shop and have them deal with it. Fingers crossed. I'd rather do it in my shed, learn, and save the money.

 

[TheDuke]

Or, you can just measure your clearance, then count how many times you have to subtract .05 before you get into range.

Is it possible to remove the shim entirely and just measure the clearance to the bucket?

 

[Big T]

Do not do that!

Call Z1, get a thin shim and use it as noted above

Steve's valve spread sheet will tell you what sizes you need.

If all the measurements show you need a 2.40 or thinner, you need to get the valves stems cut.

The bike closes clearances over time, so now's the time to prevent future head aches

 

[hotrods316]

any possibilty of just surface grinding the shims down to size and reusing them???

 

[TheDuke]

any possibilty of just surface grinding the shims down to size and reusing them???

Is that a thing shops do? I'd imagine with such tight tolerances it would be challenging to get it just right, but if it is cheaper than new $8 shims I'd be up for giving it a shot.

 

[hotrods316]

oh, 8 bucks is pretty cheap. i was brainstorming crazy ideas. i would bet my machinist would laugh at me for asking him to do it, but hey who knows, might not be too bad once you figure how to hold the shim to machine it. and they prolly are hardened or something goofy. sorry for the wild idea, unless it works then you owe me 8 bucks a shim

 

[DSM]

any possibilty of just surface grinding the shims down to size and reusing them???

I've had the same thought.

It seems like if you make sure to 'hone' the bottom side and make sure it's flat it would be an option. Then again if they are cheap and available...

 

[tkent02]

Check out the shim club on this site, a guy named Ray grinds them down and sends them out to people.

Send him your old ones when you're done.

Ray is Ghostgs1.

 

[Grimly]

any possibilty of just surface grinding the shims down to size and reusing them???

Is that a thing shops do? I'd imagine with such tight tolerances it would be challenging to get it just right, but if it is cheaper than new $8 shims I'd be up for giving it a shot.

I did that with one shim 20 years ago, when I ran out of suitable choices on a valve job in the backwoods. It's still in there. My concern was getting a nice flat face and making sure there was no bevel at all, as I didn't want it to be spat out of the bucket.
The tools? 4.5" angle grinder, pre-digital caliper and patience.

ps. I also use 2pence pieces (or suitable coinage of your country) to act as temporary shim placers if needed to turn over the engine while a shim or two is out.

 

[UK-GT]

I needed a couple of temporary shims while I was swapping them around, so I used a bit of 2mm thick aluminum plate, used an hacksaw to cut it roughly to size and then finished it with a file. It did the trick. I then worked out what ones I needed to get, I kept the ones that were the wrong size but I have still got the aluminum ones. I have since found out a friend who was a bike mechanic has got a box full of shims, but last time I checked them the one I wanted he had not got, so swapped them round again so the exhaust valve gaps are between 0.05 & 0.1 and the inlets are between 0.05 & 0.08

Oh. And make sure the shims are for a Suzuki as they are 29.5mm diameter and the ones for Yamaha and Kawasaki (I think) are only 29mm diameter and will move around in the shim bucket!!