The Moto Guzzi Colibrì was a prototype of a clip-on motor developed by Moto Guzzi during the Second World War, but which never came into production.
During the war a law was passed in Italy that made it possible to use motorcycles up to 125 cc without license plate. Moreover, there was a need for economical means of transport, because all vehicles, even trucks and tanks, drove on petrol at the time and that was scarce. A clip-on motor, mounted on a bicycle, would be ideal, because in the case of gasoline there could always be cycling.
At Moto Guzzi in 1944 the Colibrì was developed by Antonio Micucci. This was a 125 cc two-stroke engine that could be mounted above the rear wheel of a bicycle and then driven through a roller. It had, according to good Guzzi use, a reclining cylinder with the spark plug pointing forward and the carburetor with his steel mesh air filter on the back. The fuel mixture had to pass through the crankshaft and that functioned as a rotating inlet. On top of the engine was a two-liter tank and an exhaust silencer next to the rear wheel.
The Colibrì did not make the production. One disadvantage is clearly visible on photos of the prototype: the rear mudguard has expired, and that must have been quite difficult on the (mostly unpaved) Italian roads. Micucci developed after the war the 65 cc Motoleggera 65, which had much of the technique of the Colibrì, but was much more a light motorcycle than a bicycle with auxiliary engine.
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