In a motorcycle, a magneto is a device used to generate electrical power for the ignition system. It is essentially a self-contained generator that produces high-voltage electricity to create the spark needed to ignite the fuel-air mixture in the engine's combustion chamber.
Traditionally, motorcycles used magneto ignition systems, which were independent of the motorcycle's battery and charging system. The magneto consists of a permanent magnet and a coil of wire. As the engine's crankshaft rotates, it drives the magneto, causing the magnet to spin inside the coil. This rotation induces an electrical current in the coil due to the magnetic field changing with respect to the coil's windings.
The high-voltage current generated by the magneto is sent to the spark plug via the ignition coil and spark plug wire. When the current reaches the spark plug, it jumps across the spark plug gap, creating a spark that ignites the compressed fuel-air mixture in the engine's cylinder.
Magneto ignition systems have been widely used in motorcycles because they are self-sufficient and do not rely on the motorcycle's battery or charging system. This makes them particularly useful in situations where the battery is weak or has failed. However, modern motorcycles often use electronic ignition systems that rely on the battery and charging system for power. These systems are generally more reliable and provide more precise control over the ignition timing.