I'm with Glen on this. I've abused the crap out of mine, the 1,200# on a turbo flywheel. I was pulling a log up on to the road, and I had a ton of traction, (loaded with about 1000# of wet wood, and 4 low) and the clutch would not slip. All it did was stall out the motor.
Make sure that the flywheel has a 0.026 step in it. Marlin figured this out.