Andy you have put me right off putting a B33 barrel and piston onto my B31 engine, I am in the early stages of building my bike, I keep saying to myself it isn't going to be a concours winning example ( I have built these before, and have the trophies) it is going to be an old thumper to ride around the lanes, I did have a B31 swing arm model a long time ago, and it was a bit gutless, so i am thinking bump up the capacity (oh and bye the way I am not trying to emulate a Gold star, no interest) But with what you said Andy Higham, I have decided to go down the route of a T140 piston and overbore the B31 cylinder, I have 2 cylinders a small diameter fin and the large diameter fin, I'm going to use the large fin, it looks better suited to the head, I would gladly appreciate any help and constructive comments please, I am not a died in the wool BSA man, but I have always thought them solid as a rock since I had one to transport me to College in 1969, it was a C11G, what a lovely bike.
Andy I have purchased a Suzuki GS850 clutch, and would appreciate it if you could let me have some more detail of how you grafted it all together, I have a BSA centre hub, and I'm sure i have the clutch basket from an A10 or even a Triumph.
Please help