I had a chat to the right person tonight and the rubber insert that was used here (in Oz) is a part from a tractor (high density rubber) but he was trying to remember which brand it was.  Depending on the size, sometimes a thin washer is used against the engine block as well.  The torque on the front "bolt" is just starting to squeeze the rubber.  Loctite can be used on the nut whilst the rear bolt torque is still the same. 

The other option was by Luftmeister which is probably what you have in the US.  It was a cup with a rubber insert and then a washer which squeezed inside the cup onto the insert. 

I am still looking for the diagram which will be around somewhere.  I know which folder it is in, I just need to find the folder! 

I hope this helps. 

Fair enough regarding the photo. 

From what I can remember they were a hand made item to replace the washer.  I think I have a diagram from an old Club magazine, that I will try and find in the shed.  I am off to a Club meeting tomorrow and will ask around, as they were never an official part, so the origin of the modification eludes me.  The bloke who had the kits fitted them in his workshop but is now retired.  It made a noticeable difference in reducing the vibration of the engine at that certain rev range. 

The main problem is finding the correct grade and thickness of rubber, as there would have been a transfer of heat to the rubber.  If I remember correctly the torque on the engine mounting bolt remained the same.  Hopefully it should all be explained on the diagram.

Not quite sure what you are referring to as the photo is crap. 

If it is the rubber between the engine and the frame where the crash bar rear leg attaches to the frame then that is an anti-vibration modification, as the original was a metal washer.  These deteriorate over time and need replacing but I don't think this is what you are referring to    If it is something attached to the rear leg attachment nut, then just ignore it. 

Anybody know about the rubberbushib
ng ont the crashbar that attaches to the motor? It is on the leg part under the cylinder/ infront.  Probably not worth woring about but Jake was looking at it ang we both questioned it.

Thank you for the reply, waiting on mine to get out of referb jail.