About ten minutes into the helimustering flight, the engine stopped with a loud bang. A downwind autorotational approach from a low altitude was attempted. The pilot used most of the rotor's energy in stretching the glide to a small, natural clearing. The helicopter then fell from tree top height (about 30 feet) onto rocky, sloping ground. It rolled over and slid several metres down the 14 degree slope. The No 1 connecting rod had failed and breached the engine crankcase. The connecting rod had failed from fatigue initiated overload. The fatigue was initiated from a galling spot on the inside of the big-end which occurred as a result of the relaxation of the bearing nip. It is probable that the relaxation of the bearing nip was caused by repeated engine overspeeds.