Bozhou cement tanker diesel engine clutch manufacturer of a tractor Shanghai -50, after the engine overhaul, refueling mouth appeared crank chamber and the exhaust vent out power shortage phenomenon. Initially, the machine hand considered piston ring installation error or a gap between the piston and cylinder caused by too much. After checking that the piston ring is not installed wrong, the gap between the piston and cylinder to meet the requirements. Later discovered that the first piston vortex chamber has a diameter of about 1mm of trachoma. When the piston during the compression stroke, the mixed gas leak into the crank chamber, causing the cylinder will not be successful. After replacing qualified pistons, camshaft troubleshooting 4.Configurate severe wear a Shanghai -50 tractors (495A equipped with diesel engines) use two years later, no matter in what season, always start the motor with a fixed engine must be supplemented by pulling the fire started, and the machine starts to work after a serious shortage of power. By using a dial gauge to check that the intake advance angle by late posterior horn by four, the continuation of the intake valve open angle is reduced. The reason is that with badly worn camshaft. After replacing the camshaft with troubleshooting.