Hi
I have looked but the BSA gearing chart I can find is for competition gearing, what would be a good all round sprocket
combo for road use.
Ive been through this with my C15T with SS80 bottom end. If you send me your email address by private message I'll send you a spreadsheet I put together. Allows you to play with different sprocket combos and see what road speed and rpm will be in each gear.
Just looking at your rear sprocket, which looks as small as possible, I would think you have quite a high gearing. The MX or Trials sprockets are over an inch wider from the brake back-plate.