a speed limiting system particularly suited for use with magneto ignition systems for small internal combustion engines is disclosed . a shorting transistor is made conductive for a predetermined time after a first trigger pulse from a trigger coil , thus preventing subsequent trigger pulses from being effective above a predetermined engine speed . a capacitor is charged by a trigger pulse , and maintains shorting transistor conductive until it is discharged through the shorting transistor , subsequent trigger pulses arriving while shorting transistor is conductive recharging the capacitor . a diode , which also serves to prevent the capacitor from discharging through the trigger coil , provides for normal ignition system operation by delaying operating of the shorting transistor until a trigger pulse has become effective upon the gate of a scr .