Breaker point ignition systems were available in single- or dual-point systems prior to today's modern electronic ignition systems. Dual-point systems also had two ignition coils instead of one. Many older motorcycles still use point systems even though newer replacement systems are available.
The point ignition system has an ignition coil, a point cam that opens and closes the points, the points themselves and a condenser, or capacitor. The point cam is connected to the crankshaft and turns with the motor. The points are adjustable so that the spark can be timed.
How They Work
Primary voltage to the coil runs through the points. The points are closed most of the time, and this is when the magnetic field builds up in the coil. When the points open, the field collapses, and the spark is sent to the spark plugs. The condenser allows the points to open without arcing or burning. It gives voltage a place to go when the points open.
Dwell and Gap
Points must stay closed for a certain amount of time, or dwell. This allows a large enough magnetic field to build in the coil to produce a strong enough spark for ignition. The points must also be gapped at a certain distance. If the distance is too large, spark will be weak. If it is not large enough, the magnetic field in the coil will not completely collapse, producing weak spark as well. Dwell is measured with a dwell meter, and gap can be measured with feeler gauges.