Abstract: An ignition system for a small internal combustion engine is energized by an alternator which is rotatably driven in association with the engine, and ignition pulses are supplied to the engine in timed relation with the movement of a plurality of different pistons in response to trigger signals generated by a trigger mechanism. The ignition pulses are produced by a capacitive discharge ignition circuit having a pulse transformer associated with each of the different pistons, and the energization of each pulse transformer is controlled by a corresponding switch which is actuated by a trigger signal generated in an associated trigger coil by the rotational movement of a magnetic trigger rotor driven in association with the engine. The trigger rotor carries magnetic means in association with an outer member of magnetically conductive material and having an eccentric configuration defining an intervening air gap with the trigger coil which varies with the movement of the trigger rotor.