The cranks break off because people either don't take the time or don't know the 755 / 900 has a lot of torsional vibration which causes the clutch to setlleonto the crank after being installed.
Also the torque on the clutch bolt is 90 ft/lbs. Run the sled 10 minutes and retorque. You'll be amazed at how loose the bolt has become. We usually re - torque two time.