Abstract: A magneto-based, variable-timing ignition system for an internal combustion engine is provided that maintains at least one operating parameter of the engine within a predetermined limit. An electronic controller sets the timing of spark events based on engine performance criteria such as the temperature of the engine's cylinder head, speed and manifold pressure. If the values of one of these parameters, such as engine temperature, extends beyond a predetermine limit, the electronic controller retards the advance timing of the spark events to draw back within the limit the values of the parameter. The timing of spark events is ordinarily under electronic control. If the electronic control fails, the system provides spark events whose timing are fixed and synchronized to the mechanical rotation of the crankshaft of the engine.

Abstract: An ignition system is provided for an internal combustion engine that operates in two modes. In a first mode, the timing of the spark event is under electronic control. In a second mode, the timing of the spark event is fixed and synchronized to the mechanical rotation of the crankshaft of the engine. Under normal operating conditions, the timing of the spark event is electronically controlled. If the electrical system of the engine malfunctions, the ignition system defaults to the second mode in which ignition timing is mechanically controlled.