Andy, my gearbox was completely knackered with some symtoms as you describe, oil p****** out of the sleeve bearing , VIBRATION but only at times and I thought initiallyy at the time it could be the clutch out of line etc. It wasn't on striping the box everything was worn out.when rebuilt and ridden again ( only 2 weeks ago ) absolutely amazed at the difference really smooth. Also be interested to hear how things pan out re Johns comments re a bent mainshaft ,the abuse these things took in there early years beggars belief. Best wishes BobH