The magneto motor is an important electrical device for motorcycles. It is composed of a magneto rotor and a magneto stator winding. The stator winding consists of a charging winding that provides working power to the ignition system and a power winding that provides working power to the charging system. As the time a motorcycle is put into use increases and influenced by various factors, the magnetism of the magneto rotor will gradually weaken. When the magneto rotor loses its magnetism severely, it will affect the normal operation of the charging winding and the power winding, reducing the effective value of the AC output voltage of the charging winding and the power winding, thereby affecting the normal operation of the ignition system and the charging system.

The first phenomenon that emerges is the difficulty in starting the engine. This is caused by the weakening of the high-voltage ignition electric spark generated by the ignition system during the engine starting condition. Next, the battery will also experience a loss of power, which is caused by the reduction in the output power of the charging system.

Under normal conditions, difficulty in starting a motorcycle is more likely to draw the attention of drivers and maintenance personnel. Maintenance personnel will first consider that there is a fault in the ignition system and then conduct an inspection and test. They seldom check whether the magneto rotor has a demagnetization fault. Besides, in the absence of dedicated equipment, there is no very good method to check and confirm whether the rotor of the magneto motor has a demagnetization fault. In most cases, a screwdriver is used to touch the magnetic steel of the magneto rotor, and the strength of the magnetic steel's suction force is felt by hand to determine whether the magneto rotor has a demagnetization fault. Due to the lack of certain reference objects for comparison and inspection, the accuracy of the inspection and judgment is relatively low.

When the ignition system experiences weakened high-voltage ignition sparks, making it difficult to start the engine, and after inspection and testing, it is determined that there is a suspected fault in the charging winding, the first step should be to analyze and determine whether it is caused by a fault in the charging winding or a demagnetization of the magneto rotor. We can make a judgment based on the phenomenon that the effective value of the AC output voltage of the charging winding and the power winding will significantly decrease after the rotor of the magneto motor loses its magnetism.

Disconnect the connection between the charging winding connection wire and the cable harness connector. Use the AC voltage range of the multimeter to detect the AC voltage output by the charging winding. Start the engine by foot or electric start to put it into the starting condition, and record the reading of the multimeter.

If it is confirmed through detection that the effective value of the AC output voltage of the charging winding is significantly lower than the normal value, the effective value of the AC output voltage of the power winding should be measured next. Disconnect the connection between the power winding connection wire and the cable harness connector, use the AC voltage range of the multimeter to measure the effective value of the AC output voltage of the power winding, and record the reading of the multimeter.

If it is confirmed through detection that the effective value of the AC output voltage of the power winding is significantly lower than the normal value, it can be determined that there is a demagnetization fault of the magnetic motor rotor. The magnetic motor rotor should be magnetized or replaced.

If it is confirmed through inspection that the effective value of the AC output voltage of the power winding is normal, then it can be determined that the technical condition of the magneto rotor is good, indicating that there is indeed a fault in the charging winding, which has led to a weakened high-voltage ignition spark. A new charging winding should be replaced.

The advantage of doing this is that through detection and inspection, potential fault points can be identified as soon as possible and faults can be eliminated relatively quickly. If it is confirmed through detection that the effective value of the AC output voltage of the charging winding has significantly decreased, the charging winding should be replaced for comparative inspection. If the fault of weakened high-voltage ignition spark still cannot be eliminated, then check whether the rotor of the magneto has lost its magnetism, which will increase the operation time.

If it is necessary to first check whether the rotor of the magneto motor has a demagnetization fault, and when it is confirmed that the rotor of the magneto motor has a demagnetization fault, the rotor of the magneto motor can be replaced for comparative inspection. When it is confirmed that the rotor of the magneto motor has no demagnetization fault, the suspected fault point can be locked onto the charging winding, and then the fault can be eliminated, which can achieve twice the result with half the effort.

The difficulty in starting fault caused by demagnetization actually has an easier solution, which is to directly replace the DC igniter. However, if the charging is weak, there is no good solution for this.

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