Use a stepped crank from a chainsaw on karts! Machine this internal thread fitting/nut to allow use of a 5/8" bore clutch. Contributed by: Bob Blackburn And copied over from John T's McCulloch Web site

Extension shaft and clutch installed. Ideally Bob would prefer to have shown the clutch as an inboard configuration but just for these photos the clutch happened to be installed outboard. Bob had a local machine shop make this piece shown here.