A young man rode a 125 car to the front of the shop, said that he was good before this car, but in recent days, I felt that the fuel was not smooth on the way, and I could not run, and the motorcycle still had a tug tug sound.

After connecting the vehicle, test run inspection, open the electric key, start the engine for inspection, the engine is easy to start fire, idle running is good.

Slowly increase the carburetor throttle opening, the engine acceleration test, the engine working speed only improved a little, it can no longer continue to improve, the muffler also issued a "tuk tuk tuk" exhaust sound.

Since the engine failure occurred suddenly and recently, the possibility of an ignition system failure is high. Because if there is a fuel system failure that causes the engine to die, the engine will die slowly, not suddenly.

Based on this experience, the first inspection of the ignition system, no abnormal phenomenon was found, so the replacement of a variety of models compatible with Taichang Chi flitter for comparative inspection, inspection confirmed that the engine failure can not be ruled out, has nothing to do with the ignition system.

Next, the method of disconnecting the air filter and removing the muffler was used to carry out a comparative test, and the engine failure still could not be ruled out.

In the engine fault investigation, found in the engine can not be accelerated, there will be a strong carburetor back jet phenomenon, the inspection results show that the engine has a fault.

Open the valve chamber cover of the engine cylinder head for routine inspection. Rotate the magneto rotor according to the working rotation direction of the magneto rotor. During the compression stroke of the engine, align the top death center "T" mark on the magneto rotor with the timing mark of the engine inspection hole to make preparation for inspection.

First check the engine inlet and exhaust valve working clearance, the inspection results found that the inlet valve working clearance is unusually large, enough to have about 3-4 mm, and the steel ball on the exhaust valve tappet is not, so the fault situation is clear.

The root cause of the engine failure is that the working clearance of the intake valve is abnormally large, and the steel ball on the exhaust valve tapet accidentally falls off, which seriously affects the normal opening of the exhaust valve and causes the poor exhaust in the engine work, which not only causes the serious reverse injection phenomenon of the carburetor, but also makes the engine acceleration difficult fault. The reason why the owner is described as a failure after the sudden flameout of the engine, it is estimated that the flameout is related to the sudden fall off of the steel ball on the exhaust door.

Replace the exhaust valve tappet, adjust the working clearance of the engine inlet and exhaust valve to meet the technical requirements, start the engine for inspection, the engine is easy to start, the idle operation is good, carry out the engine acceleration test, the engine can accelerate well, drive the motorcycle for road test, the motorcycle driving at high speed is normal.

It is confirmed by inspection that the failure of engine to accelerate well has been eliminated.