Clutch all clean and plates oil-free once more. That still leaves the question of how the oil got in there in the first place. The O-ring in the clutch basket ‘lid’ and the oil seal on the shaft are both good.
Even though the handbook says use 20w/50 engine oil in the gearbox, I have been using modern gearbox oil, thinking I was treating the old girl to all the pampering that modern oil technologies had to offer. But still the gearbox dragged after a few miles of use and – as I found once inside – the oil was clearly getting past the seals and onto the plates.
After much head scratching it occurred to me that just maybe the modern gearbox oil is too thin for the design and so could creep past the seals. I have since filled the gearbox with fully synthetic Agip 20w/50 engine oil and the clutch works much better – no drag, neutrals easy to find, reasonably progressive when feathering. So far my individual rides have been limited to a couple of hours, but the oil has been in there for about a fortnight now and there is still no sign of the old problems.
The 2014 Lands End Trial beckons so I will soon find out if the 20w/50 trick can last for 350 miles and 18 hours of almost continuous use – assuming I am not stuck at the start with no spark like last year!