The workings of an engine are clearly explained through observing this representation four stroke petrol engine. Modeled after a typical air cooled engine, the operation of the valves is clearly evident with the cams being driven by a gear train from the rear of the main crank. A simulated spark plug uses a small lamp to indicate the firing point and a cross section of the carburetter is shown. Mounted on a base, the engine provides screw terminals for connection to a 3V battery. Size: 21 x 21 x 37 cm.