How Does Magneto Ignition System Works? Check Article Below

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In the previous article, we discussed anything about the battery ignition system, but there is another ignition system that is almost similar. Magneto ignition system, then what is a magneto ignition system? How does it work ?

In general, the battery and magneto ignition systems are the same as conventional because they still use a mechanical breaker point to induce the coil.

But the difference is located in the source of energy.

We know that the battery ignition system has an energy source from the battery, but what about small engines that don't have batteries? Where does the energy source come from for the ignition system?
chain saw use a magneto system

Then the magneto ignition system is the solution, the magneto ignition system does not require an energy source such as a battery because the power source will be generated by the engine itself.

A mini generator is connected to the engine crankshaft, it will produce electricity when the crankshaft rotates.

The excess does not require a battery, so the engine design can be very light, but for performance it is clearly less than a battery ignition system that has a stable voltage.

Therefore, magneto is widely applied to small gas engines such as chain saws, tractors, air pumps, ATVs, speed boats, motor cylcle.

Then How Does the Magneto Ignition System Work?

As always, we first discuss the components.

  • Magneto unit
  • Ignition switch
  • Breaker point
  • Capacitors
  • Spark plug


The most influence part is the magneto unit, this component not only as a provider of electric current but also has functions as an ignition coil, so naturally in this system we do not see ignition coil components such as the battery ignition system.

Magneto is basically a mini generator, which is there is a permanent series of magnets connected to a crankshaft and two coils around the magnets.

How magneto works is also the same as generators in general, when the permanent magnet rotates there will be intersection of the magnetic force lines so as to produce an electric current in the coil around the magnet.

However, there are two coils inside the magneto, namely the primary coil and the secondary coil. The secondary coil has 20,000 turns and is connected to the spark plug while the primary coil has 200 turns and is connected to the breaker point circuit.

The operational order is the magneto ignition system

1. Start when the engine crankshaft is rotated

The energy to turn the crabkshaft is obtained from an external non-electric source such as a crankshaft rotator or on the motorcycle is a kick starter.

When the crankshaft rotates magneto will produce electricity in both coils with a relatively small voltage.

Meanwhile, the ignition system need extremely high voltage. Therefore, there must be an induction process to produce extremely high voltages.

2. Electromagnetic induction to increase the secondary coil voltage

To increase the voltage to 20,000 V, it is necessary to do an induction process between primary and secondary coil in magneto.

The induction process is also the same as a battery ignition coil where the induction will occur when the magnetic field collapsed from the primary coil into the secondary coil.

To make the magnetic field collapse, the current in the primary coil must be cut off suddenly. In charge of deciding the primary coil current is a series of breaker points.

This circuit consists of a breaker contact and a capacitor.

Breaker contact is a connector from the primary coil to the ground, but this contact can be disconnected by a cam that is also connected to the crankshaft. This means that on certain timings (combustion timming) the cam will hit the breaker point and break the primary coil current.

While the capacitor is in charge of absorbing current from the primary coil when the breaker contact is open.

Capacitor is an electronic component that can absorb the current about it, when the breaker contact is still closed, the current from the primary coil goes directly to the ground but when the breaker contact is open, this current will be absorbed into the capacitor.

The main purpose of the capacitor is actually to prevent the spark on the breaker contact, that is because the gap on the breaker contact is so small that the current from the primary coil is still possible to jump.

What are the advantages of the magneto ignition system?

  • Does not require a battery
  • Light-design
  • Components are simpler and fewer


What is the lack of a battery ignition system?

  • Sparks on small spark plugs when engine RPM is low
  • When the engine RPM is high, the spark on the spark plug is also quite large
  • Need more effort to start the engine