I've had a look to investigate and here's what I've found:
- There is noticeable end float on the crank, even though the end nut is done up tight. Any end float is supposed to disappear completely with the nut tight, yes?
- The crank sprocket looks to be brand new.
- There are a couple of shims between the crank sprocket and the main bearing, however...
- The sprocket doesn't seem to go fully "home" on the crankshaft - instead, it seems to get stuck on a slight step as the splines get shallower towards the main bearing.
- There is a strange wear pattern on the back of the alternator rotor - as if it's fouling on the chain.
- Should there be a chamfer on the sprocket splines to enable it to go fully home?
- Should there be some sort of spacer between the sprocket and the alternator rotor? I can't see anything on the engine diagram.
Apologies for all the questions. As some of you may know, my bike has a rather "uncertain" history and it's sometimes difficult to sort out the normal issues from bodger-induced ones...