By listening to the tractor's abnormal sound, determine the possible failure, timely maintenance and take preventive measures. 1. Crisp knocking: The gap between the piston pin and the pin seat and between the piston and the bushing becomes large due to wear. In addition to normal wear, the oil holes in the bushing and the small end of the connecting rod are not completely aligned, resulting in poor lubrication. 2. Sudden impact noise, accompanied by white smoke from the exhaust pipe: Mainly due to valve flap vibration, falling off or falling into the cylinder due to valve spring breaking. Can easily cause damage to the piston, cylinder head, and valve guide. 3. In the intake and exhaust pipes, the sound of “click†is heard, and there is black smoke: the reason is that there is carbon deposition or burning between the valve and the valve seat, the gap between the valve and the valve guide is not correct, and the spring force of the valve spring is insufficient. Or break; valve clearance is too small. 4. After hearing an abnormal sound, the engine turns off and burns the tiles. The main reason is that the engine oil is insufficient or the engine oil is dirty and deteriorated, and the oil passage is blocked, resulting in lack of oil and poor lubrication of the bearing bush; secondly, the clearance of the bearing bush is too large or too small.