Im currently in the process of rebuilding my NSR250. My bike is a MC18 R5K however im fitting a MC28 engine from a donor bike.

My issue is while doing the waterpump I found the clutch basket inner and outer move together and do not rotate separately. The clutch plates are completely removed there is nothing left inside. If i remove the main nut both baskets rotate as expected however when its torqued up they do not move separately. Does anyone have any info whats causing this issue?