For interest - Recently I installed an extra woollen felt seal behind the clutch adaptor in addition to the usual felt seal sandwiched behind the sliding plate. It is a little thicker than the 2mm seal available from a Wales-based supplier. I thinned down a 6mm piece of felt to about 3mm. I was concerned that friction rubbing against the clutch adaptor may generate some heat, as it was never a standard part supplied by BSA. I know there are other solutions, but wanted to keep it simple.
I did a bit of reading to see if there would be any issues with friction. Apparently not.! I soaked it well with oil before assembly, and hope it doesn't spin in relation to the Inner case.
I have attached an article on theory of felt seals, a picture of the felt seal with adaptor, my felt speed calculations (xls spreadsheet page 1 including the rpm sheet on page 2 - I know you will love this GB). It seems that I would have to exceed 97 mph even with the seal dry, so no problems. My recent first outing showed no sign of a leak, the chaincase warmed only to normal temperature, and not a drop on the garage floor.
Pedantic I know but it is a cold wet day here.
Col
