Various strange noises and abnormal sound diagnosis and repair of motorcycles (below)

When the engine is working, the normal sound will be mixed with the abnormal sound. What's more, the model of the vehicle engine is various. However, as long as the engine is fully understood due to the different nature of the engine, familiar with the different sounds of different natures. The location, characteristics, timing and changing laws of the vocalization, attention to the accumulation of experience, or the accuracy, judgment and determination of the nature, location and cause of the abnormal sound.

1, the connecting rod big head bearing sound

The sound of the big-head bearing of the connecting rod caused by the sound of the big rod bearing of the motorcycle is usually caused by: poor connection between the connecting rod and the chain journal (using the sliding bearing), poor wear of the bearing (using the rolling bearing), poor lubrication, bearing bush When the welding is too tight and burnt, the operation is improper when the repair is performed, or the quality of the bearing bush is not good, the early wear and the bearing ball (column) wear, and the sound is generated when the engine is working.

Acoustic characteristics of the connecting rod big head bearing: the sound does not change with the engine temperature, and suddenly accelerates (from idle to medium speed), there is obvious continuous knocking sound (rolling bearing with internal noise of the engine), which is the main sound of the connecting rod big head bearing Characteristics: When the big-end bearing of the connecting rod is worn (loose), the engine will have obvious sound when it is idle, and the sound will increase when the load is increased. When the engine is broken, the sound will obviously weaken or disappear.

2. Valve spring knocking sound

The cause of the valve knocking sound is usually: the valve clearance is too large and the cam is worn, the profile curve is changed, the valve spring is broken, and when the engine is working, the broken valve springs collide with each other to produce an audible sound, and the valve spring knocking sound is a metal knocking sound. Continuous and messy, when the engine is broken, the knocking sound is almost unchanged. After the top-mounted valve spring is broken, there is a "dangdang" sound of the piston top colliding with the valve. When the side-mounted valve spring is broken, there is a "beep" sound, and the sound is knocked. The frequency increases with increasing engine speed, but the volume changes are not significant.

3, the piston knocks the sound of the cylinder

The reason why the sound of the piston knocking cylinder is usually that the clearance between the piston and the cylinder is too large. At the moment of the engine work, the piston is subjected to the pressure of the high pressure gas, swings in the cylinder and knocks on the cylinder wall to generate sound. In addition, the piston is reversed. Ellipse, connecting rod bending or twisting, piston pin and connecting rod copper sleeve (bearing) connecting rod big head bearing too tight, it will also cause the piston to knock the cylinder.

After the engine is broken, the knocking sound is weakened or even disappeared. When the engine is idling, the knocking sound is clear, and the knocking sound is obvious when the engine is cold. After the temperature rises, the knocking sound is weakened or even disappeared, and the spark plug hole is injected into the cylinder. A small amount (about 3mL) of engine lubricating oil, slowly stepping on the starting rod to drive the crankshaft to rotate for about 1 min, so that the lubricating oil flows into the piston and the cylinder. When the engine is working, the knocking sound is temporarily weakened or disappeared.

4, knocking caused by deflagration

When the engine suddenly accelerates or the motorcycle goes uphill, the cylinder internally emits a continuous sharp "click" sound, which is the knocking sound caused by the detonation. The knocking sound caused by the detonation is matched with the piston pin and the connecting rod small head bushing. The sound of the big voice is similar. However, the knocking sound caused by the detonation does not occur at the time of idling. When the pedal is not activated, the starting lever does not hear the sound; after starting, the sound of the piston pin is continuous and disordered, and the knocking sound caused by the deflagration increases the load and It is most obvious when going uphill, and the sound is crisper.

The causes of deflagration are: engine overheating, excessive carbon deposits in the combustion chamber, low spark plug heat value, low octane gasoline, and too early ignition time.

Motorcycle noise can also avoid part of it, as long as every car's friends are regularly maintained, and often check, the situation mentioned above will not appear on us so soon.

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