B50 Clutch

The B50 is prone to clutch slip due to the power output and the fact that the clutch was an old design originally built for the C15 250cc. The 1971 model had 5 driven plates & 4 friction (driving) plates, while the 1972 had 5 driven plates & 5 friction (driving) plates. In an effort to overcome the slippage owners have fitted an extra driven plate creating a 6 to 5 arrangement.

What should you fit? The aim is to have the clutch plates level with the clutch housing/chain wheel. Any less and you you will find the spring cups bottoming out on the retaining plate inner and the resultant clutch slippage.

Start with a friction plate. You can smear them with engine oil, which will fend off rust until you are up & running. If the final steel plate is below the clutch housing when you have 5 friction plates & 5 driven plates, then you could put an extra 6th steel driven plate on below the pressure plate so having 2 steel plates together. I believe this to be better than putting the extra steel driven plate on first (although it would give a symmetrical layout).

Beware when fitting new pattern plates as they are not as thick as the originals.