The cylinder head belongs to the valve mechanism in the internal combustion engine, which is mainly used to close the upper part of the cylinder and constitute the combustion chamber. And as the camshaft and rocker shaft and inlet exhaust pipe support. The air is mainly sucked into the cylinder, the spark plug ignited the combustible gas mixture, driving the piston to do work, exhaust gas from the exhaust pipe. Cylinder head leakage is mainly caused by the valve or the end face of the cylinder head seal. Therefore, if there is carbon accumulation on the sealing face of the valve seat, it should be removed in time. If the sealing face is too wide or there are grooves, pitts, dents, etc., it should be repaired or replaced according to the degree of the valve seat. Cylinder head warping deformation and cylinder pad damage also lead to air leakage, in order to avoid cylinder head warping and cylinder pad damage, the cylinder head nut must be tightened according to the prescribed order, tightening torque should meet the requirements.