A thread on the Gold Star Forum sent me to the "BSA" drawer of my tool chest. The factory supplied plenty of special service tools, but not all of them are available anymore, and not all jobs were covered by a special tool. Because of this, over the past ~40 years I've fabricated tools of my own to make some of these jobs easier. I know many others have done this as well, so by all means please add to this thread.
Many years ago I discovered I had tools that I had made but that I no longer remembered what they were for. So, I started writing their function on them as I made them. Unfortunately, in a few cases the paint has worn off, and in a few other cases my notation wasn't sufficiently detailed. All I know about a few tools is they are in my BSA drawer, so I probably made them for either an M21, Gold Star, or A10. However, since BSA's pre-unit singles and twins shared so much technology, there's a pretty good chance a tool I made for my M21 also performs the same function on another BSA model.
Using a socket to tighten and loosen a nut is so much nicer (and easier) than whacking it with a hammer, so the following is a socket for the shock absorber on the mainshaft.
If the spring is a bit too long to allow you to get the shock absorber nut started, compressing it a vise and using the following "C" clamps to hold it solves the problem. The clamps are made of 1/4" steel, the top and bottom of the "C" are 1/4" high, the side is 3/8", with the space between the top and bottom 1-1/8" (i.e. the compressed length of the spring is 1-1/8"). The spring is placed partway into a vise, compressed, the clamps slipped on, and the vise opened up. At this point the compressed spring is storing a lot of energy so you definitely don't want to bump the clamps while slipping the assembly together and tightening the nut.
Like the cush drive, removing the Gearbox sprocket nut cries out for a sprag socket. I made the following from a 3/4"-drive 1-1/2" socket onto which I brazed a 1/2"-drive 15/16" socket. The OD of the gearbox shaft is small enough to fit through the 3/4" hole in the first socket and into the second.
I don't remember anythng about the following tool, but what I have written on it is "M21 cam pinion post extractor (61-691)". It has a 1" ID and is 2.6" deep.
I don't remember anything about the following, but it's 1-1/2" x 24tpi and I wrote on it "Head race removal."
A Gold star has a steering stem nut with 6 notches in it. The elegant way of tightening it is with the following socket:
The following are laps for the seat in AMAL
GP float bowl. The OD of the ends that fit into the float bowl are 0.275". The larger OD at the end is what you use to twirl them between your fingers.
This is a very common tool, made by bolting together a driven and a driving clutch plate, along with an arm to hold it from moving. I made this when I got my first A10 ~40 years ago so it's pretty crude. But, it works fine, so I continue to use it.
The slots on the screws covering the clutch adjuster are pretty chewed up on many bikes because the owners don't have a screwdriver of the correct width. Also, they typically are tightened by using a hammer on a screwdriver held at an angle, which isn't the greatest way of giving them the correct torque (or keeping them looking new). Somewhere I have a "screwdriver" I made from a 1/4"-drive socket and a bar of brass of the same width and length of the slot, but I couldn't find it today. Instead, the photo is of a commercial screwdriver bit that has the correct width, that I also use.