Thanks Padmei. I am jealous of your pittance of a leak!
Mark - she's not strictly a Basic, more dolled up to look like one. Not much in it though, it's essentially the same bike.
The gearbox recently had some work done: Shorter 1st gear, longer 5th gear, machined output shaft for circlip
and new bearings and seals. And it seems there may have been a problem with the output shaft seal...
Actually, what's immediately obvious is that the machined "v" in the casing has been left open - ala the monolever bikes. They use this to vent their oil filled swingarm. Our Paralever swingarm, on the other hand, shouldn't have oil in it.