This infernal device strikes again. When Slymo mentioned the cover plate and a hammer, that threw me. On reflection I think we're talking pressure plate, and the use of a hammer to re-align the clutch basket fingers. Particularly on a used item that some miscreant has dropped, kicked and thrown against something substantial in a fit of frustration.
The other major problem with used baskets is the inevitable wear to the fingers, in the form of slots which will restrict the driving plates' movement as they lift, hence the inevitable clutch drag and hard to find/missing neutral. As mentioned, old hands free the clutch before starting up, and snick into neutral just as coming to rest. When new I reckon it would work fine, but BSA's almost universal clutch does not age well. But I'll agree with Slymo, set up properly they're OK and worth taking the time to examine every part, as all these little defects and imperfections add up.
The basic design was used across the whole model range, so correctly fitting but incorrect parts for a particular model are a potential minefield. A 6 Spring clutch complete from the C range will fit a Super Rocket, but it will slip a bit......
Adding extra plain plates and well worn ("thinner") lined plates were another old trick to increase spring tension and friction capacity, back when the new bits were scarce/pricey. Looks like room for another plate, I have found that pattern plain and lined plates can be considerably thinner than the originals.
Swarfy.