A magneto is a compact, reliable electrical generator that powers small gasoline engines without a battery. Commonly found in lawn equipment, dirt bikes, mopeds, jet skis, outboard motors, and RC model airplanes, it delivers short, powerful electric pulses ideal for igniting spark plugs and driving internal combustion.

Unlike an electromagnet, which creates magnetism by passing current through a coil, a magneto produces electricity by moving a coil within a permanent magnetic field. The core components are: the armature (typically U‑shaped) bearing a thick primary coil and a finer secondary coil; a flywheel fitted with two strong magnets that generate the magnetic field; and an electric control unit—often a breaker and capacitor—that interrupts the field to release the generated current.

When the flywheel turns, the magnetic field sweeps across the armature’s coils, inducing voltage in the primary coil. A cam in the control unit momentarily contacts the armature, breaking the field and producing a voltage spike. The secondary coil, wound more tightly, amplifies this voltage before it’s routed to the spark plug. The cam then disengages, the field rebuilds, and a new pulse follows—each cycle taking only a fraction of a second.

For proper engine operation, the magneto’s spark must align with the piston’s compression stroke. In larger engines a distributor historically timed the spark to each plug, while modern systems use electronic ignition units for greater precision.

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