Here are the photos of the crankshaft clutch arrangement most of which I think are self explanatory. I'll take some more shots of it as I re-assemble it on the crankshaft. I'm taking the opportunity to replace the 2 bearings, the needle roller S2016 and the thrust bearing which I think is a LJ 5/8 (the existing bearing markings are not clear). When I stripped the clutch down I noticed that as well as the repaired crack, the drive pulley has a piece missing from it and whilst this may not cause any major problems it could cause undue belt wear. So I may make a new drive pulley / clutch arrangement from a standard pulley welded to a piece of 6" diameter x 1/4" thick steel for the clutch drive plate and to make fitting it easier mount the whole assembly using a taper lock.