Up until about two weeks ago the clutch on my Matchless G3 has been fine, but now it's having problems. When I first start it after it being stood for a few days, I put it into gear and let the clutch gently out, but it just lets go all in one go as though I've just let the lever straight out and the bike leaps forwards. After it's done this and got it out of its system, all seems fine. It seems odd as the clutch opens up and lets me put the bike into first gear and only after this does it act up and it just does it the once when I first start off. I've had a look and everything seems fine, plates look OK and there is plenty of oil, but something must be wrong or sticking somewhere, any ideas chaps?
Loose clutch hub nut or loose mainshaft nut. Burman clutches are one of the best designed of the lot except for the splines wearing in the hub if left loose.