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

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 had a stripped thread in a cast iron cylinder head so I've had the hole welded up so that I can drill and tap a new thread. Unfortunately I can't make much of an impression on the weld. I'm using a 2mm cobalt drill bit in a pillar drill. What do I need to drill this really tough steel and then my next problem will be can I cut a thread?
Hoping someone is knowledgeable to point me in the right direction.

Has anyone got any suggestions for a modern equivalent spark plug for the old KLG L777 fitted to many BSAs in the 30s?
Would a Champion L87 do the job?
Cheers

With new kickstart bushes fitted, I've carried out a dry run of reassembly. With the inner case fitted without a gasket, there's significant endplay in the mainshaft. There's a thrust washer inside the inner gearbox case. Are different thickness of thrust washer available, or shims, or is there something else that could be an issue?
Many thanks in anticipation.

Can anyone suggest what the thread is where the advance retard cable screws into the magneto body (Lucas M01)? At first glance its about 7/16" diam and 26tpi. BSCy ? Its not the cable thread that's stripped, that would be an easy fix, but the female thread in the magneto body!!!

Yes, I'm still having fun trying to get my B21 deluxe together. The latest issue is that the carb is correct ie an amal 275 and the magdyno seems correct, but when the carb is fitted, the edge of the dynamo hits the float chamber bolt, preventing it from being tightened and seating correctly. Both parts can be fitted but not together. Am I missing a trick here. You can't raise the carb or lower the dynamo and the only solution I can think of is to fit a spacer on the inlet manifold which will reposition the carb further away.

I've just been chatting to a mate on the phone whose got a weird problem. His A50 hasn't been started for a few months, its got a nearly new premier carb, new fuel pipes and fresh petrol. If the pipes are disconnected from the carb and the taps are opened, fuel flows from the open ends. If the pipes are connected to the carb and the tickler depressed, the carb will not flood and the bike won't start. He's removed the carb and given it a thorough clean. There are good blue sparks from boyer ignition. So, what could prevent the carb flooding when the tickler is depressed? Any ideas?

The restoration of my B21 continues. Inside the timing chest, the timing gear plate has a bronze bush which doesn't have a shaft running through it. Is this correct?
Behind it is a nut with locking washer that sits proud and causes the plate to rock slightly. The nut has chewed the inner side of the bush. Something is not quite as it should be. Any advice would be appreciated.

B and M group bikes of the late 30's had an oil filter in the oil tank, part no 66-8323. I'm guessing it slipped over the oil return pipe with a flange sitting in the neck of the filler. I can't find a supplier. Can anybody point me in the right direction or post a photo with the dimensions so that can can make one?
Cheers

Its slow progress with my B21 restoration. The more I uncover the more I find dodgy work. So what's new. I'm not aiming for a show bike but need it to work and get me from A to B.
As the gaskets for the covers of the gearbox are no longer available, can anyone suggest the thickness of the material I should use to make my own?

The wheels and spokes on my B21 have been changed at some time in the past. The diameter of the spoke is about 3mm or 1/8". Two of them are loose and won't tighten. If I can extend the thread a couple of mms it should get it sorted. Can anyone give any suggestions to what the thread is likely to be?

My B21 restoration continues. Unfortunately so far very little is being restored and there are more and more parts needing restoration. So far I've drawn a blank with the kickstart bushes, so I may be looking for someone to make them.
Whilst working on the front brake I noticed a lot of movement in the top girder link. The parts book lists fork bushes 65-5078. Can anyone advise whether these are associated with the top link of the late '30s 'B' series?
Many thanks in anticipation.

As you may gather, I'm getting stuck into getting a B21 deluxe up and running. There is distinct play in the kickstart and in my innocence I removed the gearbox outer cover expecting to find a bush for renewal. There was just a bush for the gear lever which is good. The parts book lists kickstart quadrant bush 65-3116 and cover bush 65-3134. Are these both behind the inner cover?
There was no outer cover gasket, just sealant. Am I correct in thinking that there should be gasket 65-3022? All good fun.

I have a rather sad looking speedo drive from a B21 in need of tlc. It has a cork to prevent dirt getting into the mechanism. Presumably there was a removable cover originally to allow access to the gears for lubrication. I anyone able to shed any light on the subject?
Cheers

I can see the 1938 parts lists in Library search but does anyone do a parts book with exploded views, so you can hopefully see which part joins to which in these prewar bikes?

I'm looking at the feasibility of restoring a B24 basket case. Can anyone advise on the possibility of finding a cylinder head and front forks, plus some hen's teeth if pos.

I've just removed the piston from my 1950 B33. It's a heplex 11341 with maximum skirt diameter around 86.4mm. There are no markings to indicate whether it is standard, +20, +40 etc and would like to fit new rings.
Does anyone know what size it's likely to be?
Can anyone suggest where I might obtain some rings?
And when I reassemble, should the split in the skirt be at the front or back, or doesn't it matter (it was facing the front)?
Cheers

There is a very audible click when the exhaust valve on my 1950 B33 fully opens. With the plug out, and with the rocker cover and tappet adjuster cover removed, by turning the back wheel in top gear its difficult to tell where the source is. Sometimes I can see a definite twitch of the tappet accompanying the click as the pushrod goes over the top. I am suspecting that the problem is at the bottom end ie cam and or cam follower. I'm betting that this isn't going to be an easy fix. Any thoughts would be appreciated.
Cheers

The primary chain tensioner on the B40 is simple and effective. However, the chain slides over the steel surface of the tensioner gradually wearing grooves and releasing particles of steel into the primary case which in turn increases the wear of chain and sprockets. The primary chain, sprockets and tensioner can be regarded as renewable service items. As far as I can remember, the surface of the A50/A65 tensioner is a hard rubber material and nylon is used on other brands. Has anyone tried a modification to reduce the steel on steel wear that has proved effective?