market dynamics
What's the reason why the motorcycle is so loud? What's wrong with the motorcycle?
Release date:2020.03.26

When a motorcycle is running, it often makes all kinds of noises. A motorcycle that works properly allows a certain amount of noise. But when a mechanism failure, cause abnormal sound, if not timely maintenance, it is easy to accelerate the wear and tear of the parts or damage, shorten the service life of the motorcycle.


The main reason why motorcycles are too loud

1. Carbon accumulation blockage -- removal

2. External cracking due to corrosion or collision -- welding repair

3. Pressure death of internal muffler filter cotton -- restructuring or lengthening

4. Open welding of inner partition -- disassemble and repair welding

5. Loose connection between exhaust pipe and exhaust duct of cylinder block -- tighten screw or replace interface pad

6. Abnormal combustion -- check fuel and oil lines or electricity

7. Loud noise may be a problem with the exhaust pipe, see if there are cracks.

8. Check the carburetor for slowness on the throttle.

9. The motor vibrates a lot. If the motor vibrates when refueling in neutral, it must be the engine's problem. If the vibration in the process of driving, see whether the front and rear wheel bearings are aging, the fixing screw is loose.

The cause of abnormal noise caused by motorcycles

The piston is banging on the cylinder

The clearance between the piston and the cylinder is too large, when the engine is working, there will be a large sharp tapping sound, sudden acceleration or reduce the sense of "click" sound. The noise is most pronounced when the engine is cold and accelerating, and decreases when the engine is running at a higher temperature.

Check as follows

(1) before starting the engine, continue to tap the starting lever, generally can not hear the tapping sound. But when the start, suddenly accelerated, it will occur "click" sound, that is to knock the sound of the cylinder.

(2) remove the spark plug, inject about 1/20 liter of oil into the cylinder, step on the starting lever several times, and then start the engine, such as noise reduction or elimination, is caused by the piston and cylinder wall gap is too large oil temporarily filled. But after a few minutes, the oil gets hot and thins out, and the noise still appears.

(3) with a long screwdriver (or a metal rod), one end of the contact with the upper part of the cylinder, the other end close to the ear, you will hear the "tap" tapping sound. Sometimes as a result of repair the connecting rod small head cover and piston pin, assembly is tight also can produce knock cylinder sound, but this kind of sound is more depressing, and generally is after the car starts to happen.

The tapping of a piston pin

Plug pin and connecting rod small head or piston pin and piston pin hole with too large clearance, piston up and down movement caused by radial tapping, produce a clearer "click" sound. This noise is usually apparent at high speeds and in sudden acceleration. Delay the ignition and the noise will be slightly reduced.

Check the method

If you do not start the engine, you will hear a "click, click" sound in the cylinder when you continuously tap the starting lever. After starting the engine, make the engine idle, the screwdriver will touch the upper part of the cylinder, with the ear side to listen, there is a clear "click" sound.

Knock caused by deflagration

When the engine accelerates suddenly or the motorcycle goes up the hill, the cylinder interior sends out continuous and sharp "tap" sound, namely the knock sound caused by deflagration.

The knock caused by deflagration is similar to that caused by the piston pin and the connecting rod small head bushing fitting clearance. However, the knock caused by deflagration will not occur at idle, and the starting lever can not hear the sound before starting; After starting, the noise of piston pin is continuous and disorderly, and the knock caused by deflagration is the most obvious when the load is increased and the hill is up, and the sound is clearer.

The causes of deflagration are as follows

(1) low octane gasoline is used;

(2) premature ignition time;

(3) overheating of the engine;

(4) excessive carbon accumulation in the combustion chamber;

(5) low calorific value of spark plug.


Between the cylinder and the cylinder head, between the cylinder and the crankshaft box or the crankshaft box, if the fastening bolts are loose or the gasket is damaged, there will be a "haw" sound of air leakage. After starting, the sound is not easy to hear when running at uniform speed; When stopped for inspection, visible traces of oil can be found from the leak. If this phenomenon is not serious, just tighten the fastening bolt can be, serious should be replaced gasket.

The tapping of the valve

If the valve clearance becomes larger due to improper adjustment or wear of parts, the valve mechanism will produce short and sharp knocks. The tapping does not vary with the speed of rotation. Can be eliminated by adjusting valve clearance or replacing worn parts.

Piston ring noise

If the piston ring torture, insufficient piston ring bullet, piston ring ring or piston ring gap, side gap, back gap is too large, when the engine running, the explosion of gas will be rushed down, rushed into the crankcase surface to give a sound of air leakage. Touch spark plug with screwdriver, listen carefully, have clear "bang, bang" sound.

The big end of the connecting rod bearing

When connecting rod big end bearing and bearing hole excessive wear or assembly clearance is too big, crankshaft rotation will produce radial impact and a heavy "thud-thud" sound. Idle running sound is obvious, in the high - speed running noise is mixed and not easy to identify.

When checking, do not start the engine first, continuously tap the starting lever, will hear "cluck, cluck" sound; After starting, when idling, touch the lower end of the cylinder with the screwdriver and listen with the ears.

Tap on throttle of carburetor

The throttle valve is constantly moving up and down in the mixing chamber. Due to excessive wear and tear, the clearance is too large. Due to the impact of airflow, the throttle valve produces radial swing and hits the mixing chamber during the air inlet stroke of the engine. This sound in the idle when almost no sound, the throttle to 1/4 open the maximum sound, and then increase the throttle, the sound gradually reduced, when the throttle to the end, the sound disappeared.

When checking, can use screwdriver to hold carburetor to listen, in the throttle to 1/4 open, there is a clear tapping sound. Can also be removed from the air filter, with fingers against the throttle, the tapping sound disappeared, relax the finger tapping sound again, can be identified as the throttle tapping sound.

Carburetor temper

Backfiring occurs in two situations. One is when the engine starts, it makes a "snap" sound from the air filter and emits a whiff of white smoke. The other is a sudden "snap" from the air filter when the engine is working.

There are several reasons why the carburetor backfires at startup

(1) the mixture is too thin;

(2) premature ignition time;

(3) the spark plug spark is weak;

(4) the contact gap of the breaker is wrong;

(5) water in oil;

(6) the oil road is blocked;

(7) the intake valve of the four-stroke engine is burned out, and there is no gap between the intake valve and tappet.

The carburetor suddenly backfires while the engine is working. The reasons may be as follows:

(1) the engine load is too heavy and the gear is not cut in time;

(2) the capacitor is damaged or in bad contact;

(3) the mixture gas is too thin due to the oil road jam;

(4) four stroke engine inlet valve suddenly bite dead, etc.

The exhaust pipe let off the gun

Exhaust pipe discharge also occurs in two cases, one is due to the engine is not working properly, so that the combustible mixture in the exhaust pipe combustion explosion and "crackle" sound, sound crisp, loud, at the same time emit sparks or smoke; The other is due to the rupture of the muffler itself, so that part of the high-pressure exhaust gas directly into the atmosphere and produce a "crack" sound, the sound is weak, disorderly and uninterrupted.

In the former case, the cause of discharge pipe blasting is:

(1) the mixture is too thick;

(2) ignition time is too late;

(3) gasoline deterioration or moisture;

(4) capacitor damage;

(5) four stroke engine exhaust valve bite or valve clearance.

As a result of the muffler break and release sound, generally can only be re - welding, if the muffler tail opening is too large, can also use pliers to open the opening to close the opening a little.