Switch
The ignition switch, also known as a screw switch, is a component of the ignition system of internal combustion engines, and is used in older motorcycles in particular. Its role is to control the precise moment of ignition by opening and closing the electrical circuit between the ignition coil and the spark plug. Here's how a switch works in the context of a motorcycle:
How it works : The ignition switch operates mechanically and is usually coupled to the engine crankshaft. It features an eccentric cam which, as it rotates with the crankshaft, pushes a set of open and closed contacts.
Positioning : The ignition switch is usually located near the engine camshaft, where it is activated by a cam mechanically connected to the crankshaft.
Ignition timing: When the eccentric cam reaches its highest point, the switch contacts close, allowing electric current to flow from the ignition coil to the spark plug. This creates a spark that ignites the air-fuel mixture in the cylinder.
Current interruption: the eccentric cam then pushes the switch contacts open, interrupting the electrical current. This interruption generates a high voltage in the coil, ready for the next ignition cycle.
Wear and maintenance: Switches can wear out over time due to mechanical wear. It was common practice to adjust or replace them periodically to maintain optimum ignition performance.
Evolution to electronic ignition: Modern electronic ignition systems have largely replaced mechanical switches. These systems use sensors and electronic circuits to control ignition more precisely and reliably.
Adjustment: In switch-based systems, adjusting the ignition timing was an essential task for optimizing engine performance. This involved adjusting the distance between the switch contacts at a specific point in the engine cycle.
It's important to note that most modern motorcycles use electronic ignition systems, eliminating the need for mechanical switches. The advantages of electronic systems include greater precision, reduced maintenance and increased reliability.
