Skytrax CNC-machined one-piece adapter replaces the stock PTO crankcase cover with a bolt-up facing for the Rotax C gearbox, or Rotax E.  Critical alignment ring is integrated for excellent wear characterisitcs for all shaft couplings, including Mohawk GT5 sprag clutch, RK400 cetrifugal clutch, and Mohawk "Big Boy" 78mm rubber donut (replaces Rotax 76mm donut which does not hold up to 100+HP applications.)  Additional Rotax gearbox custom machining is required to fit all applications.  

SkyTrax RX1, YG4-Rotax C box adapter