How to solve the abnormal noise of motorcycle exhaust pipe

1. Knocking sound of carburetor throttle: the throttle keeps moving up and down in the mixing chamber, and excessive wear leads to excessive clearance. In the intake stroke of the engine, due to the impact of airflow, the throttle swings radially and hits the mixing chamber, which will make a "giggle" sound. You can hardly hear this noise when idling. The noise is maximum when the throttle is turned to 1/4. When the throttle is increased, the noise gradually decreases. When the throttle is turned to the end, the noise disappears.

2. Air leakage sound: If the fastening bolts between the cylinder and the cylinder head, between the cylinder and the crankcase or between the left and right crankcase are loose or the gasket is damaged, it will make a "chirp" air leakage sound. After starting, the noise is not easy to hear when running at a constant speed; When stopping for inspection, obvious oil stains can be found from the air leakage. If this phenomenon is not serious, just tighten the fastening bolt; if it is serious, replace the gasket.

3. Valve knocking sound: If the valve clearance becomes larger due to improper adjustment or parts wear, the valve mechanism will make a short and sharp knocking sound. This kind of knocking does not change with the change of speed. It can be eliminated by adjusting the valve clearance or replacing worn parts.

4. Piston ring noise: If the piston ring is tortured, the elasticity of the piston ring is not enough, the piston is surrounded by death, or the clearance, side clearance and back clearance of the piston ring are too large, when the engine is running, explosive gas will rush down quickly and rush into the crankcase, giving off a leaking knocking sound. Touch the spark plug with a screwdriver and listen carefully. There is a clear "bang, bang" sound.

5. Noise of connecting rod big head bearing: The connecting rod big head bearing and bearing hole are excessively worn or the clearance is too large during assembly, which will produce radial impact and make a heavy "thump" sound when the crankshaft rotates. The noise is obvious when idling, and it is difficult to distinguish when running at medium and high speeds. When checking, don't start the engine first, and press the starting lever continuously, and you will hear the sound of "click, click"; After starting, when idling, touch the lower end of the cylinder with a screwdriver and listen with your ears. There is an obvious "da da" sound.