I'd change the oil pump drive cog (one with the the two lugs) and get one of the small 'cushions' that fit into the hole in the clutch basket where the oil pump fits to.
There should be a washer that goes on the main gearbox bearing, then the oil pump drive, then the clutch basket, bearing, spacer. The washer with the slot should go next, slot facing in towards the clutch basket. Then the inner basket, tab washer and nut! fit the plates and other bits job done.
If you start replacing parts such as the pump drive or the main basket check for play as later bikes had a small shim to give a set tolerance that was not present on the early models like yours.
Suzuki mad
GS1000E 1981
GSX1100ESD 1983 Fully functional (Boy it's quick!)
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