There's a 1/2 locknut on both sides of the front wheel on mine but the forks aren't original. You can therefore adjust the bearings on the bench and when the wheel is fitted, the wheel nut tightens against the fork and locknut. I don't think there are locknuts on the back. With the wheel nuts loose, you need just a hint of play in the bearings. Now tighten one wheel nut without the spindle or wheel turning. Does the wheel lock? Now do the same with the other side. This will give you an idea if one or both of the adjusting cones are problematic. If so, you might have to slacken a cone a little, and tighten the wheel nut, playing around until the wheel turns freely with just a little play. The wheel nuts need to be tight and against the chain tension adjusters. Hope that sorts it.

Check my article re B21 wheel bearings in this months Star. If the brake side bearing isn't tight at the end of the spindle thread, there's a possibility that when you fit the wheel nuts, you'll tighten the bearings. If set up correctly, you should be able to tighten the nuts without affecting the bearings. How do the bearings feel with the wheel off the bike?
Another possibility is that somehow you're brake is being applied. Will the brake lever move?

You may be tightening the bearings when you tighten the wheel nuts. Are you using ball and cup bearings or taper rollers, and are they correctly adjusted?

For parts lists have a look at https://bsa-info.nz/parts-lists/#Various.
Once you've got to 'parts lists' go to 'various' and there are many old lists in year order.

After more digging I've found that most of the various gearchange parts for the B21, M20 and B33 etc have the same part numbers, apart from these elusive springs fitted in 1939. I couldn't find the part numbers for the B21 pawls. It doesn't make sense. I've photographed the stripped gearchange to see if any eagle eyed viewer can see anything wrong. The only suspect area might be the reprofiled pawl ends. Mine come to a point whereas pictures online show them as rounded.

According to the 1939 parts book, all models were fitted with the same gearchange springs 66-3224 and 66-3225. They were changed for 1940 and the earlier ones appear to be no longer available. The shorter one on my B21 is incorrect and cobbled together to provide tension. Does anyone know a source for these springs or failing that, what the dimensions of the short spring would be? I'm guessing around 47mm long, 8mm diameter and 7mm end loops.
Cheers
Paul

After a bit of research I think that the UNF is a squared off thread and the BSCy is rounded. If that's the case with everything else being equal, a 1/2"x20 BSCy bolt would be tight going into a UNF nut and if it's the other way around, it would probably be an easy fit and possibly weaker. Some of the taps advertised are simply marked 1/2"x20. I phoned one supplier to ask about this and they told me that they supply the UNF tap for both threads.
So, I agree with the above comments, always use the correct tools, and make sure you insist on it being correct.

I've a 1/2" x 20tpi BSCy thread that needs cleaning up. I've a 1/2" x 20tpi UNF tap but somewhere at the back of my mind I think there's a small difference in the thread which affects the strength if the two are mixed. Does anyone have an opinion on this?

I've had a few fins repaired over the years. The last time the welder used 3mm sheet steel to fabricate the missing piece of fin and I think the key is to use a high chrome welding rod. By welding it, the fin will then act as a cooling surface as originally designed. Its obviously a lot easier if the broken fin is at the end of the row.

Hi Guru
There's plenty of choice around but I've just fitted a Yuasa 6N6-3B-1 to mine.

Have a look at Andy Tiernan's bikes. There are photos of a 1939 B21 deluxe with sidestand.

I took the photo from the web.
It's certainly possible to fit one, but it's a bit awkward. There're plenty of after market ones available. You need to know the diameter of the frame tube that it'll clamp onto and the length needed to allow the bike to lean a few degrees. The brake anchor strap is a bit in the way. If the stand angles forward during use it will help prevent the bike rotating around the stand.
If you have a go, let us know how you get on.

Yes he spent a fair bit of time getting things lined up and clamping it absolutely solid. He said that the drills were designed for removing broken taps. Impressive. I didn't know such things existed. It's good to keep learning.

Update: had a go with cobalt drills and they just blunted. Had a go at annealing by heating it up until it was red then cooled over 1 1/2 hours, but still just as hard. My engineer friend said that martensite had probably formed during welding and the way to sort it was to heat it to 800' for three days then cool it very slowly. That wasn't going to happen, so I took it round to his workshop and over an hour he gradually drilled it with some very special carbide drills. So job sorted.

I thought I'd seen one somewhere. Its a bit tricky and has to be quite far back, so don't know how stable it'll be, but it's possible. You might need to braze/weld the clamp to the frame to stop it turning and dropping the bike on the floor.