Gotta give those good vibrations.

Find out if they have been converted to the vernier type, if so, look up in the manual (under electric start Mk3)  how to adjust. If they are still the original type you are adjusting by shims. You might have worn out, crumbling isolastic rubbers. If so, its time to replace them. Some replacement iso rubbers are miles too hard leading to a vibey ride.

Badly worn isos can let the engine/primary case touch the left hand aluminium footrest plate so transmitting vibes to the frame        

Andover Norton are the best bet for correct rubber spec. This is based on many, many feedback comments in the last few years I have read on various forums etc . The front ones are more important for vibes, and much easier to swap.

   I would fit the vernier system if not already there.

In answer to your question, more information is needed, peel back rubber on other side and send a pic so we know what you have. While exposed try a 0.010" feeler gauge between End cap of tube and abutment, don't be surprised if it will not go in.

Sounds like you have no end float or replacement rubbers that are too stiff. A good test is to try levering between lower frame rail and engine, it should be easy to raise and lower it 1\4", if not you need more clearance.

Let us know how you get on.

Regards Martin

Don't think I'm any the wiser from your picture, although I'll take a stab at pre-Mk3.

The gap is specified as 0.010" (10 thou) or 0.25mm. You can go a little tighter on the rear to sharpen up the handling.