I just bought myself some work

The last owner of the bike started to disassemble the starter/starter clutch but never got it Working.
I'm looking at it now and find the construction a bit trippie.
This is the old model starter clutch with the starter gear in two pieces, exactly how does
The gear and the gearhub connect? Should they be a really tight and connect by just friction?
The reason I'm asking is that the hub has sized to the axel and and both the gear and gear hubLooks like they might have been pretty warm, and might have worn down.
Is it possible to find a new brass-bearing for the hub or would it be best to try to find a whole "new" one? I probably need to measure the axel before reassembly to, the oil seal seem to wobble when the axle is turned (looks very beaten up to)
Any other tips and tricks are well welcome