Was a bit surprised I don't need Cork sleeve behind clutch I suppose that should be good news in some ways. However, oil has been getting in the clutch but maybe not so much from this direction. The domed clutch cover gasket was very poor so maybe that's where the oil got in.
As noted elsewhere this bike is a bit of a mongrel with a few odd parts. I thing even the gearbox is not standard, as although not used, it has a speedo drive coming out of the casing and 3/8" final drive chain. So... tempted to leave the chain case as is. After al, it fits fine and looks ok.