market dynamics
The motorcycle suddenly made a strange noise and became very noisy,What's the matter?
Release date:2019.10.23

A common problem with noisy motorcycles

1, carbon blockage - removal

2, rust or collision and external cracking -- welding repair

3. Internal muffled filter cotton is pressed to death -- reformed or lengthened

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

5. The exhaust pipe is not tightly connected with the exhaust duct of the cylinder body -- tighten the screw or replace the joint pad

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

7, the sound may be the exhaust pipe problem, see whether there is a crack.

8, throttle slow, check the carburetor, throttle cable.

9, motorcycle vibration, if in neutral during refueling vibration is certainly the engine problem. If it vibrates during driving, check whether the bearings of the front and rear wheels are aged or the fixing screws are loose.

The unusual noise of a motorcycle


1. Piston knocking on cylinder

The gap between piston and cylinder is too large, when the engine is working, it will produce a larger sharp knocking sound, suddenly accelerate or reduce the feeling, the "click" sound occurs. This kind of sound is most obvious when the engine is cooling and accelerating.

Check as follows

(1) before starting the engine, step the starting lever continuously and generally no knocking sound can be heard. But when it starts up and accelerates suddenly, it makes a "dada" sound, which is the sound of knocking on the cylinder.

(2) remove the spark plug, inject about 1/20 liter of oil into the cylinder, step the starting lever several times, and then start the engine. If the sound is reduced or eliminated, it is because the gap between piston and cylinder wall is too large and the oil is temporarily filled. But after a few minutes, the oil gets hot and thins, and the noise continues.

(3) with a long screwdriver (or a metal rod), one end of the screwdriver contacts the upper part of the cylinder and the other end is pressed against the ear, and a tapping sound of "da da" is heard. Sometimes because repair connecting rod small head cover and piston pin, assembly is tighter also can produce knock cylinder sound, but this kind of sound is more depressing, and it is when repair car starts commonly, ability happens.

2. The knock of piston pin

The gap between the plug pin and the small head cover of the connecting rod or the piston pin and the hole of the piston pin is too large. This noise is usually more noticeable at high speeds and sudden acceleration. The ignition time will be delayed, the noise will be slightly reduced.

Check the method

Do not start the engine, continuously tap the starting lever, you will hear a "click, click" sound in the cylinder. After starting the engine, make the engine idle, the screwdriver will contact the upper part of the cylinder, with the ear side listen, there is an obvious "click" sound.

3. Knock sound caused by deflagration

When the engine accelerates suddenly or the motorcycle climbs the hill, the cylinder interior gives out the continuous sharp "click" sound, that is, the knock sound caused by deflagation.

The knock caused by deflagration is similar to that caused by the large gap between the piston pin and the bushing of the connecting rod's small head. However, the knocking sound caused by deflagration will not occur during idle speed, and the sound cannot be heard by stepping the starting lever before starting. After starting up, the sound of the piston pin is continuous and disorderly, while the knocking sound caused by deflagation is most obvious when increasing the load and uphill, and the sound is clear.

Causes of deflagration

(1) low octane gasoline was used;

(2) premature ignition time;

(3) engine overheating;

(4) excessive carbon accumulation in combustion chamber;

(5) low calorific value of spark plug.


4. Air leakage

Between the cylinder and the cylinder head, between the cylinder and the crankshaft box or between the crankshaft box and the left and right crankshaft boxes, if the fastening bolts are loose or the gaskets are damaged, there will be a "haw" leakage sound. After starting, it is difficult to hear the sound when running at a uniform speed; During stop check, obvious oil stain can be found from the leak. If this phenomenon is not serious, just tighten the fastening bolt. If it is serious, the gasket should be replaced.

5. Valve tapping

If the valve clearance is enlarged due to improper adjustment or wear of parts, the valve mechanism will make a short and sharp knocking sound. The stroke does not vary with the speed of the revolution. It can be eliminated by adjusting valve clearance or replacing worn parts.

Piston ring noise

If piston ring torture, piston ring spring is insufficient, piston ring encirclement or piston ring notch clearance, side clearance, back clearance is too large, when the engine is running, explosion gas will be rapidly channeled, rushed into the crankcase surface to give out leakage knock sound. Touch the spark plug with the screwdriver, listen carefully, there is a clear "bang, bang" sound.

7, the big end of the connecting rod bearing sound

Connecting rod big head bearing and bearing bore excessive wear or assembly clearance is too large, the crankshaft rotation will produce radial impact and send out a heavier "da dong" sound. Idling when the noise is obvious, in high speed when the noise is disorderly and not easy to identify.

When checking, do not start the engine first, step the starting lever continuously, you will hear the sound of "cough, cough"; After starting up, when idle running, use the screwdriver to contact the lower end of the cylinder and listen with the ear, there is an obvious "ta ta" sound.

8, carburetor throttle knock

The throttle keeps moving up and down in the mixing chamber. Due to excessive wear, the gap is too large. During the engine's intake stroke, due to the impact of airflow, the throttle generates radial swing and hits the mixing chamber. This sound in the idle branch turn almost can not hear, throttle to 1/4 of the open degree when the sound is the largest, then increase the throttle, the sound gradually decreased, when the throttle to the bottom, the sound disappeared.

When checking, use the screwdriver to listen to the carburetor. When the throttle is added to 1/4 open, there is an obvious knocking sound. Can also remove the air filter, with the finger against the throttle, knock sound disappeared, relaxed finger knock sound again, can be determined as the throttle knock sound.

9, carburetor tempering sound

The tempering noise occurs when the engine starts up with a "pop" sound from the air filter and a puff of white smoke, and the engine is difficult to start. The other is the engine working suddenly from the air filter issued a "pop" sound.

The cause of the carburetor tempering at startup

(1) the mixture is too thin;

(2) premature ignition time;

(3) weak spark of spark plug;

(4) the contact gap of the breaker is not correct;

(5) water in oil;

(6) the oil road is blocked;

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

There are several possible reasons for the sudden tempering of the carburetor when the engine is working

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

(2) capacitor damage or poor contact;

(3) the oil road is blocked so that the mixture is too thin;

(4) the intake valve of a four-stroke engine suddenly bites to death.


10. Sound of exhaust pipe release

The exhaust pipe release gun also occurs in two situations, one is due to the engine working, so that the combustible mixture in the exhaust pipe combustion explosion and issued a "splat" sound, sound clear, loud, and emit sparks or smoke; The other is due to the rupture of the muffler itself, so that a part of the high pressure exhaust gas directly into the atmosphere and emit a "snapping" sound, its sound is weak, disorderly and uninterrupted.

In the former case, the reasons for the exhaust pipe shooting are as follows

(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 dead or no valve clearance.

Because silencer is broken and produce put gun sound, can weld afresh commonly only, if silencer tail opening is too big, also can use pliers to open the opening to clip a few.