What is a points ignition system on a vintage Harley-Davidson motorcycle?

Points ignition systems were once a common type of ignition system used on vintage Harley-Davidson motorcycles. These systems use a set of mechanical contacts, known as "points," to control the flow of electricity to the spark plugs and ignite the fuel-air mixture in the engine's cylinders.

In a points ignition system, the points are mounted on a cam that rotates along with the crankshaft of the engine. As the cam turns, the points open and close in a repeating pattern, allowing a current of electricity to flow through the ignition coil and to the spark plugs.

The points are held closed by a spring and are opened by a cam follower, which is a small metal rod that follows the contours of the cam. As the cam follower rides up and down on the cam, it pushes against the points, causing them to open and close.

The timing of the ignition system is controlled by the position of the cam and the points in relation to the crankshaft. If the points are not correctly timed, the spark plugs may not fire at the optimal time, leading to poor engine performance or even engine damage.

Overall, the points ignition system on a vintage Harley-Davidson motorcycle works by mechanically opening and closing a set of points to control the flow of electricity to the spark plugs and ignite the fuel-air mixture in the engine's cylinders. Proper timing is essential to ensure optimal engine performance.