A scooter propulsion system is provided both as a kit for retrofitting and as an improved original manufacture. A foot pedal pivots forwardly and rearwardly as the user presses on a front foot pedal portion and rear foot pedal portion, respectively. A ratchet bar is pulled forward when the front pedal portion is pressed and rearward when the rear pedal portion is pressed. A free-wheeling sprocket-like gear on the rear wheel axle is rotated forward by rack-like ratchet bar teeth when the ratchet bar is pulled forward thus engaging spring pawls of the rear wheel axle gear with a rear wheel hub. A ratchet bar guard biases the ratchet bar against the rear wheel axle gear. When the rear pedal portion is pushed the rear wheel axle gear freewheels backwards as the ratchet bar moves rearwardly. A smooth portion of the ratchet bar rests against the rear wheel axle gear when the rear pedal portion is pressed to its down position.