Before putting my gearbox back in the bike it occurred to me that this would be a good moment to check on the Isolastics. On removing the nearside shim carrier, etc., I found the outermost rubber bush cocked in the cradle tube, as shown in my first pic.
My first thought was that I had somehow managed to displace it while driving out the mounting stud, but once the bush was removed from the tube it seems clear that it must have been sitting cocked in the tube since first fitted about five years ago (second picture).
I might of course have fitted it as found, and I usually have little difficulty in accusing myself of incompetence, but it is difficult to see how one might either achieve this result or overlook it if nevertheless accomplished.
However, if this is not the case the only remaining possibility is that it became cocked in service — something I also find difficult to account for. Any suggestions?