BSA M33 Gearbox Build

Detailed look at removing stripping and diagnosing a gearbox problem.

[@perrystalsis55]

I had a 1955 M33 back in the late '70's, your video is making me want another one! 😊

[@dominicthompson9096]

Thanks for the video, very helpful

[@chrislaunders8283]

I think you have to remove the speedo drive to extract the layshaft, your kickstart ratchet gears are very worn, replace them.

[@ianwright3971]

Interesting, your gearbox has the main case from an earlier WD box with later internals and outer covers...No mention of the fact that the shafts should be shimmed correctly during assembly which is an important omission....

[@750triton]

Where did you get the adaptor hub for the Triumph clutch please? I've only found one for the A10, which has a different main shaft taper. I need one for a B33 which has almost the same gearbox as yours

[@peterashley6257]

Sorry! The part came with the bike. Can’t help, I am afraid. Good luck!

[@hunterjamison4808]

I replaced worn bushes and a worn gear in my ‘51 zb31. I’m hoping I got the spacers correct. I’d heard that you check end play with out the gaskets. Did you replace the worn gear?

[@allenhanford]

When you say that the kickstart "slips" was there mechanical grinding that would indicate a problem with gears? I'm writing this as I prepare to fix the kick start on my BSA B33 but the slipping on it is smooth. That makes me to think the clutch is to blame.

[@peterashley6257]

It was clear to me that the slippage was in the gearbox, and not getting as far as the clutch. I could feel an initial resistance on the k/s which sometimes was good and started the bike. Other times there was a slight graunch and the k/s pushed down without the clutch spinning. As I am sure you know, if you experiment with the p/c case open it will be clear.

[@Cobra427Veight]

Did you have any trouble getting hold of all the parts required ? .My b33 gearbox doesn't have too many issues ? , maybe an extra neutral , but I have a weird cyclic vibration , there were issues in the primary which I thought might fix it , like very tight chain , clutch basket out of alignment, worn triumph basket etc , ive made it better but it's still there a little bit , I was wondering if the bushes or bearings in the box are bad , I did find one other thing , the exhaust was jammed hard on the foot peg lug . I need to test ride see if that made a difference, Have you ever had anything similar ? Cheers

[@peter2ym8]

BSA boxes generally are considered pretty robust. They have not had excessive power through them! Also I was told by someone older and wiser that these old 4 speed boxes should be nice and loose to work smoothly. So don't over engineer new bushes to 001" clearance. I needed a couple of new pinions because the dogs had worn and the "dovetail" no longer held the gears when engaged. Ebay is your friend. I found what I needed in Australia (I am UK based). The parts arrived in 10 days, and not expensive. Having said that, I have always managed to get parts I needed from UK suppliers.