What causes abnormal noise in a newly replaced motorcycle motor?

[OJulian]

The abnormal noise in a newly replaced motorcycle motor can be attributed to the following reasons: Excessive clearance between piston and cylinder: The knocking sound from a newly purchased motorcycle engine is usually caused by excessive clearance between the piston and cylinder. During the power stroke of the engine, the piston is subjected to high-pressure gas forces, causing it to oscillate and knock against the cylinder wall, resulting in noise. Additionally, issues such as piston ovality, bent or twisted connecting rods, excessive tightness in the piston pin and connecting rod bushings (bearings), or big-end bearings can also lead to piston knocking. Problems with the ignition system: If this occurs, it is recommended to check the ignition system and fuel supply system. If the starter can operate normally, it indicates that the battery has power. Motorcycle engines are equipped with an ignition system, whose main components include the ignition coil and spark plug.