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Ignition - As old as the combustion engine

An internal combustion engine must have an ignition system, in short: an ignition. Glow-tube ignitions used at the beginning of automotive history were so unreliable they were quickly replaced by electric ignitions. The gases in the engine's cylinders are ignited by an electric spark.

What does an ignition consist of?

The ignition includes the electrical and electronic components involved in generating the spark. There is a power source, an ignition coil, spark plugs, cable connections, and a part that switches the ignition coil. In the simplest case, this is a mechanical switch called a breaker; in an electronic ignition, it is a complex circuit. The switch is mechanically coupled to the engine via a cam or electronically via an encoder. This ensures that the ignition spark always occurs at a specific time (ignition timing) at the end of the compression stroke.

How does an ignition work?

The spark that ignites the fresh gases drawn into the cylinder is nothing more than a discharge with a very high electrical voltage. We don't get very far with the 6 or 12 V provided by the batteries. Low voltage is turned into high voltage with a transformer. The ignition coil is such a part. There are two windings in the ignition coil, one for the low voltage and one for the high voltage. When low voltage current flows through the low voltage coil, a magnetic field builds up. When this current is interrupted, the magnetic field collapses and at the same time produces the desired voltage for the spark plugs in the high voltage coil. The electrician says the voltage is induced. This voltage is conducted via the ignition cables to the spark plugs, where it jumps between the two electrodes as a spark.

What types of ignition are there for Harleys?

Depending on the type of power source, there are two types of ignition: Magneto ignition and battery ignition. In magneto ignitions, the current which the breaker switches is generated in the device ("magneto") itself by a magnetic rotor in the coil. When the breaker switches, the high voltage is also generated in the coil, which then goes through the ignition wires to the spark plugs and jumps at the spark plug.

In battery ignition, the current comes from an external source, a battery. With battery ignition, the ignition coil is controlled either by a breaker or electronically.

Harley-Davidson V engines with ioe valve activation came from the factory with either magneto or battery ignition. Magneto ignition disappeared in the 1930s. From then on, street models were only available with battery ignition. Magneto ignition was again available from the Motor Company in the 1940s for racing models and later in the Sportster C and CH models. In the custom scene magneto ignitions were adapted for other street models. Hunt and Morris magnetos proved to be significantly more reliable than the Lucas magnetos used by the British competition.

What is the ignition timing? What do I have to adjust?

The ignition timing is the moment when the spark jumps between the two electrodes of the spark plug. Since a mechanical switch like the breaker is subject to a certain amount of wear, the switch must be checked at certain intervals and readjusted if necessary. First, the distance between the switch contacts is adjusted, and then the position of the breaker in relation to the cam. With an electronic ignition, there is actually nothing to readjust. It is only adjusted once during installation. The electronic encoders themselves are wear-free. In the event of a malfunction, however, the only option is replacement. While the condition of a breaker can also be seen, faults in the sensors can usually only be detected with a measuring device.

Have any questions?

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