My B31 rigid is a bitsa and in no way oem (it has a bob newby belt drive). The gearbox is not great and doesn’t really suit the bike given its power upgrades (to maybe 25hp, and 90mph now). Its got a huge gap between 2nd and 3rd, and a very slow change.
I think the C series 4 speed gearbox has the same internals as the A series and can be adapted to suit the B31 rigid frame, but I have not found one (in nz) despite looking on/off for years, but I DO already have a spare A series plunger gearbox (so a bolt on type) and I am wondering if anyone has used that as a basis for an upgrade to a B31?
Or any other suggestions?
