hi, can anyone tell me if my 1954 bsa b31 plunger engine is covered by the haynes pre unit singles manual, I am trying to remove the clutch to get at the gearbox sprocket and I can't undo the centre nut, it doesn't help that some previous owner has welded what looks like the tab washer, I have managed to chop the weld but the nut although loose on the gearbox shaft will not undo, I don't think it's a left hand thread, any advice appreciated