1. Continuous knocking occurs between the tail end of the valve rod and the driving part when the valve knocks at the engine idle speed. It increases with the speed of the engine, and the engine temperature changes or when the fire is broken, the sound is not changed. The main reasons are as follows: (1) adjusted valve clearance is variable (locked, wear between valve stem and drive part) and valve is not adjusted well. (2) wear of valve adjusting screw, loosening of locking nut, excessive or inconsistency of valve clearance. (3) the valve spring seat is worn and grooved, and the valve stem and the pipe wear too much. Processing method: re adjust the valve clearance. If the locking nut of the adjusting screw is loose, it should be locked to replace the worn parts. 2. The gas valve leakage is sound outside the valve door, which is more obvious at the high load and low speed. The noise is enhanced with the increase of the load. The main reason is that the valve seat is skewed or the valve gap is small because of the improper operation or the wear of the inner hole of the valve tube in the reaming valve seat, which causes the valve to be ablated and caused by the valve to be ablated and the valve is closed and leaking. . Disposal method: remove cylinder head, grind valve, check valve spring elasticity, re adjust valve clearance. 3. The valve spring is broken and should be replaced. 4, the valve seat rings, the surface of the seat ring is rough, the machining precision is unqualified, the interference of the seat ring is unsuitable to loose the loose, the material is unsuitable after the heat and the valve seat inserting technology is not required. Processing method: re fit the valve seat according to the assembly process requirements, the upper end face is flush with the body plane, and the higher part must be leveled.