Where can I find a table showing markings for the B31 and B33 con rods? I have looked but unable to find any thing.
Pre 1953 both B31 and B33 con rods were 7 3/8 inch long. Post 1953 the B33 rod was 6 7/8 inch long the B31 stayed at 7 3/8 inch. Early rods 65-483 late rods 66-1614.
can anyone confirm these numbers?
my BSA parts list has B31 as 66-482 and B33 as 65-1613. My list does describe them as "conrods with bushes" so that may be different to any numbers cast onto the rods alone.
cheers
Thanks both for the info but am slightly confused, it doesn't take much. My con rod is still fitted to the flywheels so I cannot measure them. The flywheels are marked 66-635 and the con rod 65-1614. Does this make it a post 1953 crank?
you can still measure the rod. Just take the measurement from the centre of the big-end pin on the outside of the flywheel to the centre of the small end.
That should get you close enough to tell the B33 rodS apart (if it comes out at 8+ inches you have aN M20/"1 crank as they used the same flywheel castings, just machined differently to the B33)
If it is marked 65-1614 then it is a late B33 rod this will need a late piston. This has the gudgeon pin about half inch below bottom ring. If right under bottom ring then it is an early piston.