Originally Posted by
edbeek
I don't know exactly what it is either, but if that's a chain drive sprocket behind the nut, well it's knackered.
Does the clunk at the bearing come from inside the bearing or between the bearing & shaft because there looks to be a gap there. If so the shaft may be worn or it's the wrong bearing.
If you can see any of the thread at the end of the shaft at all you should be able to work out if it's left hand or right hand thread. If not, try both ways carefully. I'd guess Left hand thread.
If you can't undo the nut because the shaft wants to turn too, grab onto that worn sprocket with a set of stilsons as i'd imagine it would be splined onto the shaft.
Hope that helps.