Shim question

[Guest]

Never seen this asked directly, but if it has, I apologize!

If I cannot get my thinnest feeler gauge in, how do I know how far to reduce my thickness? How do I know it wouldn't close further yet if the cam wasn't there??

Short of swapping shims in and out (that most of us don't just have a bunch of extras laying around to test with), what direction should I head?

Thanks-

[Triam]

depends on what's happened to your bike. If you've got the valves and seats cut then you need to go quite a few sizes down. If you're just checking the clearances then you should only have to move 1 or 2 sizes.

[Triam]

if you can still rotate the shim in the bucket, but you can't get your smallest gage in then you know that there's clearance, but that it's still out of spec. You'd only need to move one size smaller.

[xxBenJamminxx]

If possible take one out and put a coin in there to hold its spot and then try the next one. Not all the shims will be the same thickness so try and see if say number 1 exh has a 2.70mm shim try to find another valve with like a 2.65 or 2.60mm shim and replace the coin with one of them. Then you can measure and see where your at. NEVER REMOVE A SHIM AND ROTATE THE ENGINE/CAM!!! Always have at least a coin in there to prevent damage to the cam, bucket, etc..... Lastly, obviously be sure you removed the coin and replaced a shim prior to starting.

[Nessism]

This is a very common topic. The clearance reduces with mileage and eventually all goes away, burning the valves shortly thereafter.

You need a thin checking shim, 2.30 for example. Install thin shim, measure clearance, calculate actual shim need, and place order.

As mentioned, never rotate engine without a shim installed.

[FLHGSRay]

This is where I whip out my .001 shim stock. Most of the feeler gauges are thicker than .001, and this could save you swapping in a test shim. It worked on my 2 tightest valves, telling me I had at least some clearance. Any machine shop will have it, and likely give you a piece. Make your own .001 feeler gauge.

[MatBirch]

Thanks everybody. I'm on it!