I just picked up a 9 tooth IAME sprocket which seems to have a fixed copper bushing fitted inside. Does this really go straight onto the crank with no roller bearing? Some sites say the bushing is required and some say a special washer and bolt is required? Anyone ran one of these that can shed some light?
It should still need the roller bearing I believe. The special washer and nut are the replacements to the regular ones that go onto the crankshaft. The washer and bolt have to be machined down for chain clearance so that the chain doesn’t hit them and come off.