Abstract: A motorized bicycle includes a gasoline powered trimmer motor that is mounted on the rear of the bicycle. The flexible drive cable of the trimmer motor is coupled to a first overrunning clutch by a vertically-oriented gear system that includes a worm and a worm gear. In turn, the first overrunning clutch is coupled via a chain and sprocket system to the conventional chain ring of the bicycle, and a second overrunning clutch is likewise coupled to the chain ring of the bicycle to couple the pedal shaft of the bicycle to the chain ring. Each overrunning clutch includes a central shaft having four pawls, and five reciprocating spring-loaded plungers surround the shaft and selectively engage the pawls every 18.degree. of shaft rotation.