Hi
I've acquired a 1948 BSA M21 for a project, more on that and some photos in a separate post late, but it's for a speed trial, obviously not one that involves too much actual speed... I'm trying to get my head around what I have and don't have. The bike was described as a barn find, and whilst largely complete is short of a few things, rear mudguard, it's supports, rear chain guards, regulator, most of the wiring and toolbox are the main items. To help I've got some parts books. But that's where my question comes. As far as I can tell what I have is reasonably original but with parts missing, but doesn't fit into either the 1948 parts book I have or the 1949-195? Parts book. What I have appears to me to be telescopic forks and frame but perhaps using up the stock of gearboxes so having a rear wheel speedo drive not the integral drive with the later gearbox. The actual drive is missing but the wheel appears ready to accept it and the cable from the speedo reaches where it would need to, I think.
The frame number is YM20 T 3768 and engine YM21 1702. The 'T' doesn't seem to figure in the lists of numbers, but the numbering looks valid and makes sense as T for telescopic. I've also seen photos of restored 1948 M21's with the the same gearbox/speedo setup. A six spring clutch is fitted, although someone has welded a nut for a large bolt in the place where a smaller bearing thingy would be pressed in and where I think SRM offer an improved adjustable arrangement. Rear wheel is the riveted non-QD style, front brake 7" with the spigot to engage with the fork slider matching hole. Tappet cover has stacked guns emblem and timing cover has the round winged emblem.
I'm just wondered if any of you had encountered this before? As the project isn't to restore to original none of this really matters, but I also don't want to prevent or make harder that as a future option, which is partly why I'm trying to better understand what I have.
Cheers
Richard
email (option): Dickie.bobbie@hotmail.co.uk
This particular specification was produced for a short period of time only...
Telescopic forks were introduced just over half way through the 'model season' but the bikes still had the WD type gearbox without a speedo drive...The later box was introduced for the following year...
As they had now lost the front wheel drive for the speedo, for around 4 months the speedo drive was fitted to the rear wheel...
This rear wheel was as you describe...Therefore not the WD type but with the brake drum riveted to the hub and the speedo drive added...
The winged BSA logo was introduced for '48 and the front brake is correct for an M20/21...
I used to have an M33 to this spec....Ian
Hi Ian
Many thanks for the confirmation and details.
Yes the riveted rear hub will need some attention, the sprocket teeth looked worn, ie hooked, so ideally need renewing, which is going to be a tricky process. The bearings for the rear had some play too. I'm going to be busy
Cheers
Richard
email (option): Dickie.bobbie@hotmail.co.uk