Hi Reidoz,
Firstly I applaud you for still using a "Supercut" as they are the Rolls Royce of Scott Bonnar cylinder mowers, but sadly were surpassed by the model 45 due to it's much lower weight factor and ease of operation. I am shortly going to embark on a full strip down / rebuild of my all original unit that I picked up for $20 just over a year ago. At this point I haven't investigated the clutch arrangement so I can't give you anything positive but I'm sure that there are a couple of guys on here that have some more experience with them than I have at this stage.
Please don't be discouraged at this point as I'm sure one of our senior members will chime in soon.
Cheers,
BB