How does a magneto work?
Most small lawn mowers, chain saws, trimmers and other small gasoline engines do not need a battery. Instead, they actually generate the power for the spark plug using a magneto . Magnetos are also used on many small airplanes (for example, the Cessna 152 seen in How Airplanes Work ) because they are extremely reliable. The idea behind any ignition system is to generate an extremely high voltage — on the order of 20,000 volts — at exactly the right time. The voltage causes a spark to jump across the spark plug’s gap, and the spark ignites the fuel in the engine. See How Car Engines Work or How Two-Stroke Engines Work for details. The magneto is the white block in the following photo (this is the magneto for a chain saw ): The idea behind a magneto is simple. It is basically an electrical generator that has been tuned to create a periodic high-voltage pulse rather than continuous current. An electrical generator (or a magneto) is the reverse of an electromagnet (see How Electromagnets
