I have a 1946 B31 with a badly worn rear sprocket. The sprocket is integral to the riveted up hub, and replacements appear unobtainable. Is there another wheel that will fit?
The M20 wheel looks similar, and the brake drum/sprocket bolts on, does anybody know if they are interchangeable?
All advice is very much appreciated.
If you are against a wall, you could try machining off the old sprocket and weld on a new 42T ring. However heat from the welding may cause distortion.
I have a 1949 B33 plunger and for whatever reason, it had a 46T rear sprocket which I believe was fabricated per the above because this does not exist in the parts book. I replaced the brake drum/sprocket with a 42T assembly. This is different from your configuration however.
I've said before, a decent engineering machine shop could sort.
We used to have a Sykes v160 hobber, as long as they have a hob with right dp etc they can cut otherwise with today's cnc technology a vmc or HMC cnc controlled could profile mill..
The final option is as on our B40 get a bigger sprocket get bored out to take top diameter of your teeth and bolt through the teeth. It worked on a racing b40.
Final option, contact someone like Talon who make sprocket.
There is a guy who can repair it for you, he turns off the old one, welds a new one on and machines it, so you can't see the joint, think he is called John Hemmings, he is in OBM, he did mine, lovely job and a lovely fella.
Occassionally reasonable ones do turn up on the likes of ebay. I bid what I considered a high price on a complete hub about a year ago and still didn't win it. I think it went for over £200. Glenn
My M33 started life as an M20 ridged. A previous owner had converted it to an M33 fitting all B33 parts including a B33 rear wheel. If a B33 wheel fits a M20 frame so maybe a M20 wheel will fit a B33 frame.