Does anyone know where I can get a 300 x 20 Avon Speedmaster ribbed tyre?

Can anyone explain the design of the Clutch Hub Bearing?
1932 models had 2 identical brass? rings (15-307 Clutch Ball Retainer) to hold the balls, but in 1933 BSA changed one of them to a thicker ring (15-306 Clutch Ballrace Ring).
I assume the thinner ring goes on first? Can anyone confirm?
Regarding fit, it seems clear neither of the rings should rotate on the hub, so an interference fit would be needed on the hub. The inner one could probably be a light interference fit (to allow for removal), but what about the outer ring? If this were an interference fit, it would be necessary to adjust it's position carefully, to give the necessary clearance to allow the balls to rotate. Maybe just push it hard on and then back it off tad? It probably wouldn't back off squarely.
Neither of my rings are an interference fit, but the outer ring has never moved outwards allowing the balls to drop out, in thousands of miles, even though- if loose- there is nothing to stop the ring moving.
Does anyone have any thoughts on this?
 

I wonder if any of you experts out there can help me with an explanation of the Blue Star lubrication system?
I see there is a pressure relief valve, which BSA call an oil feed ball valve, mounted horizontally in the timing cover.
It also has an oil pump bypass plunger and spring in the oil pump.
I assume that the ball valve operates in the same way as a normal Pressure Relief Valve, in that when the oil is cold and thick, the pressure is higher, and so pushes the ball valve off it's seat, allowing some of the oil to bleed off, thus reducing the pressure. However, I can't work out where this oil goes to. It doesn't go back into the sump, as there is no cross drilling. If it is directed into the timing case, this would just fill up with oil.
Also, can anyone confirm that the Bypass plunger in the oil pump is there to prevent excessive pressure and possible damage to the pump, in the event of a blockage, by recirculating the oil within the pump?
Can anyone confirm my thoughts, and does anyone know where the oil from the relief valve goes?

Has anyone got any idea where I might get an MP40 headlamp (or even just a picture)?
I believe they were 6 1/2".
Back in 2018, Hans posted that he had one, but I imagine that's too long ago now.
Steve.

Hello,
I've just joined, and I wonder if anyone can help me?
I have a 1933 B33-3 Blue Star Junior. Am I  right in thinking that the back wheel should be in line with the frame rear downtube? Does anyone know what the rim offset should be, or is the rim centred on the hub grease nipple?
I may have the wrong rear sprocket fitted as it is solid, without the large radial holes (as on the Sloper). It's 42T, but the dishing may be wrong. Any ideas?
I think the rear hub adjusting sleeve  (27-6714) fitted is also wrong, as it sticks out about 1/4" more than either the Sloper or B2, and doesn't look right.
Does anyone out there have one of these machines? Unfortunately BSA redesigned both the engine and frame for the 1934 season, but I think it's the same as the '30, '31 and '32 250's.