1. The engine stop switch is malfunctioning

A motorcycle with an engine stop switch will shut off when a short circuit occurs. Identify a short circuit not caused by human factors and replace the flameout switch.

Second, the voltage stabilizer is faulty

The voltage stabilizer has a low withstand voltage capacity and is burned out at high voltage. It should be replaced with a voltage stabilizer rectifier with a high withstand voltage capacity.

Three, check if there is no oil left

You must be thinking, "Stop it! How could you not know that the problem of running out of fuel is so simple and it's already on the dashboard?"

No, no, no. I really didn't make a fuss. Once, when I was almost out of gas and the dashboard showed it, I forgot to refuel because I was too busy. Then, while waiting for the traffic light at the intersection, the engine suddenly stalled and wouldn't start. The editor was so foolish as to start several times at the intersection, and the cars behind kept honking.

Finally, realizing that the fuel was running out, I quickly opened the spare fuel tank... I believe this is not just me!

Before the fuel runs out and the engine is turned off, the engine speed will suddenly increase automatically (the throttle handle has not been pressed). This phenomenon is easily felt when driving at low speeds. At this time, stopping the car and checking if there is any fuel in the fuel tank can confirm it.

Four. The fuel supply cannot be normal

This situation is that before parking, you will feel a lack of power and it will gradually decrease, and then it will gradually stop automatically.

At this point, after confirming that there is oil in the fuel tank, check if there is any oil in the carburetor.

If there is no oil, it indicates that the oil passage from the fuel tank to the carburetor is clogged and should be cleaned and unblocked.

If the carburetor is filled with oil but the vehicle still cannot be started, it is necessary to check whether the oil filter of the carburetor is clogged and whether there is any dirt in the main orifice.

Even if it can start, it doesn't mean the matter is settled. It indicates that there is a fault in some part of the fuel system that has not been detected. The fuel supply system's pipelines must also be thoroughly unblocked. Otherwise, it is possible that the fault of the engine automatically stalling will occur again.

Five. The engine temperature is too high

Excessively high temperatures and poor lubrication can cause the piston and cylinder to seize up, which can also lead to engine stalling.

The signs before the engine stalls are that the power gradually decreases at first, and then it suddenly stops.

After a confirmed diagnosis, the first step is to check if there is any lubricating oil in the crankcase. If there is not much or no lubricating oil, then check if the oil pan or the oil drain plug is leaking oil. After identifying the problem, deal with it properly and then add the specified amount of lubricating oil.

If it is not a problem of oil leakage, it is necessary to check whether the lubricating oil has been consumed excessively and add or replace the lubricating oil in time.

Six. The clutch or other parts are stuck

When the screws on the clutch support disc are not tightened and the safety riveting points are not properly punched, failing to play a safety role, the screws become looser and looser during engine operation, causing the screw heads to press against the bearing cover plate of the transmission pair shaft, resulting in the clutch getting stuck and unable to rotate, which leads to a sudden stop.

When encountering such a situation, first remove the transmission and then eliminate it based on the looseness of the clutch.

When the gears of the transmission are broken and their fragments get stuck in the transmission, or when the transmission chain loosens and gets stuck at the main shaft sprocket, it will cause a sudden stop.

So when the engine suddenly stalls, one should first identify the problem and then eliminate it one by one.

Vii. Circuit Faults

The automatic stop caused by a sudden power outage in the circuit will not show any abnormality in the engine before the sudden stop.

The causes of sudden power failure in an engine usually occur on the lines, such as loose or disconnected joints, cut wires, short circuits, etc.

For instance, if the ignition coil is faulty, it might be due to the ignition coil connector being loose and causing the flame to break. One should inspect each connector, remove the oil stains, increase the clamping force of the connector plate and seat, and enhance the contact strength to ensure stable contact.

The trigger coil is faulty, and the lead joint of the trigger coil is loose, resulting in an open flame. The welding strength of the lead should be strengthened, and the risk of false welding should be completely eliminated.

Therefore, the steps to check for faults are:

First, check the battery wiring and all the wire ends of the low-voltage wires. Then, check whether the high-voltage wires have fallen off from the spark plugs and the ignition coil ends. Verify this with a spark test.

When the battery power is exhausted or the connecting wires are loose but not disconnected, it can also cause the engine to automatically shut down. However, the signs before shutting down are different from those of a sudden circuit break.

At the beginning, the engine will fluctuate up and down, and the motorcycle will jolt. When the throttle is reduced and the engine speed drops, the engine will automatically shut off.

This is because when the engine speed is high, the generator supplies power for ignition, and the engine still keeps running. When the speed changes, the output current of the generator also changes, causing the ignition to be interrupted and the motorcycle to start. When the throttle is reduced, the engine speed drops, the generator fails to generate electricity or the current is small, and the spark plugs cannot ignite, forcing the engine to shut down.

At this point, first carefully inspect the condition of each wire connection to ensure there is no looseness. Then measure the battery power and charge it as per the specified requirements.

Engine stalling caused by rainwater seeping into the fuel line:

The fuel line is our common name. Generally, the formal term for it is the fuel supply system, which mainly includes several major components such as the fuel tank, carburetor, and air filter. Rainwater mainly seeps in through three channels:

1. Seep into the fuel tank from the fuel tank cap and then flow into the carburetor;

2. It is drawn in from the air filter intake port and eventually reaches the carburetor.

3. Enter the carburetor directly from the vent pipe of the carburetor itself.

The most likely possibility is the third one, which is also the one I have encountered most frequently in actual maintenance. Almost 80% of engine stalling in the rain occurs when rainwater enters through the vent pipe. The first two possibilities are only theoretical and are not very common in reality.

Rainwater entering circuit-type flameout: Here, the circuit mainly refers to the ignition circuit, including charging and pulse coils, electronic igniters, high-voltage packs, high-voltage caps, spark plugs, and an flameout switch. The high-voltage caps and flameout switches are the parts where rainwater is most likely to enter. Occasionally, there are a few igniters and high-voltage packs with poor moisture-proof performance.

In fact, the engine stop switch has the function of being waterproof and moisture-proof. However, there are still a few engine stop switches that cannot withstand the penetration of rainwater, causing a ground short circuit (referring to short-circuit engine stop switches) and causing the vehicle to stall.

Rainwater entering the fuel line and the electrical circuit can both cause a vehicle to stall. However, before the engine stalls, some of their symptoms are different. Based on these symptoms, it is convenient for us to roughly distinguish whether it is rainwater entering the fuel line or the electrical circuit.

When a vehicle is in normal driving and suddenly feels unable to refuel, the speed slows down relatively evenly, and the engine stops after a few seconds, this situation is mostly due to water entering the fuel line.

When a vehicle is running normally and suddenly its speed drops sharply, the driver feels a distinct jolt and the engine stalls quickly (about 1-2 seconds), this is usually due to water entering the circuit.

Another situation is that when the vehicle is driving normally, it suddenly fails to refuel. The exhaust pipe makes a long "puff, puff" sound with a gap, as if the engine only starts once after a few turns. After a period of time, it eventually stalls. This is also a symptom of water entering the circuit.

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