Its not unusual to get some wear on the inside of the clutch cover, although yours seems a bit excessive. Often times the retaining clip will get weak and slip out of the groove, allowing the driver to wander on the shaft and possibly grind the chain on the cover. There is a spacer that can be used in place of the retaining clip. I don’t know the part number, but its an IAME part.
KartLift Kart Stands
DeepSeat Kart Seats
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