Uploaded October 2025 | Updated September 2026, 1 week ago
The G.P. 500 (acronym for Guzzi - Parodi) was the first prototype motorcycle built by Carlo Guzzi and Giorgio Parodi; built in 1920, it preceded the foundation of Moto Guzzi by a year. It contains many innovations that characterized all the models of the Casa dell'Aquila for over forty years. Carlo Guzzi, passionate about engines since he was very young, decided, on the eve of the outbreak of the First World War, to create a motorcycle that was able to eliminate all those defects that he had seen many times on those he worked on in the Ripamonti workshop in Mandello in Lario, assisted by Giorgio Ripamonti, the town blacksmith. The project, developed during the war years while he was serving as a seaplane engineer marshal of the Royal Navy, found support in close friendships with two pilots of the 260th Squadron, Giovanni Ravelli and Giorgio Parodi, to whom he showed his ideas, and the three decided who at the end of the conflict would have collaborated to carry out the project: Carlo Guzzi would have taken care of the construction, Giorgio Parodi, belonging to a wealthy family of Genoese shipowners, would have financed the undertaking, and Giovanni Ravelli, a valid motorcycle racer already known before the war , would have been the driver who would have promoted the motorcycle on the race grounds. Unfortunately Giovanni Ravelli died in an accident during a test flight on 11 August 1919: it was in his memory that the Eagle with spread wings was subsequently introduced as the Moto Guzzi trademark, the emblem of the Naval Aviation. The prototype, built in 1919 in the Ripamonti workshop in Mandello del Lario, with the approval (and economic funds) of Giorgio's father, Emanuele Vittorio Parodi, presented numerous practical, as well as rational, technical solutions, some deriving from the aeronautical sector. The prototype, despite having passed the tests brilliantly, turned out to be too mechanically complex, expensive for mass production and also too futuristic: thus the Normale, the first motorcycle produced by Moto Guzzi and put on sale in the first months of 1921 differed from the prototype in various details, including the ignition system (replaced with a single spark plug) and the distribution (replaced with one with two opposed valves). The name was also changed: the acronym G.P. it could easily be exchanged with the initials of Giorgio Parodi alone, and therefore the name Moto Guzzi was introduced. The engine, a 500 cm³ single-cylinder four-stroke (displacement then considered medium-small, but capable of offering considerable performance for market needs), was horizontal, facing forward, thus exposing the cylinder head - the hottest point of the engine - directly into the wind of the march; the bore/stroke ratio was 88 x 82 mm, therefore super square, a solution never adopted in the motorcycle field at the time, which allowed, in addition to the adoption of larger diameter valves (with therefore advantages for performance), the use of a shorter and less stressed connecting rod due to the lower speed of the latter. The distribution, with four parallel overhead valves controlled by an overhead camshaft in turn driven by a shaft and bevel gears, combined with the recall of the valves with needle springs and the double ignition controlled by a single Bosch magneto (which guaranteed excellent combustion of the mixture in such a large combustion chamber, given the super-square bore/stroke ratio), were applications of aeronautical origin, learned during service on the seaplanes of the Royal Navy during the war. To reduce vibrations and obtain greater robustness of the crank mechanism and crankcase, a large external flywheel was installed on the left side of the engine (which became the symbol of Guzzi and ironically called the "slicer"); the aluminum crankcase contained both the crankshaft and the gearbox, so as to use a single lubrication circuit and eliminate the primary chain, using instead a pair of helical tooth gears. The gearbox was thus in direct drive, resulting in the engine turning in reverse with respect to the wheels, a considerable advantage for lubrication, as the oil leaking from the connecting rod head was projected onto the upper wall of the cylinder, which by gravity fell onto the lower one, which would not have been possible with normal rotation, causing the oil to end up directly at the bottom and leaving the upper part dry. To improve the stability of the motorbike and the driving comfort, also taking advantage of the engine which was not very developed in height, a very low frame was created, with an under-barrel tank, with a continuous double cradle, shock-absorbed at the front with a parallelogram fork and rigid at the rear. The very low compression ratio, of 3.5:1, also limited by the quality of the fuels of the time, was still capable of developing around 12 HP and taking the motorcycle to 100 per hour.
The G.P. 500 (acronym for Guzzi - Parodi) was the first prototype motorcycle built by Carlo Guzzi and Giorgio Parodi; built in 1920, it preceded the foundation of Moto Guzzi by a year. It contains many innovations that characterized all the models of the Casa dell'Aquila for over forty years. Carlo Guzzi, passionate about engines since he was very young, decided, on the eve of the outbreak of the First World War, to create a motorcycle that was able to eliminate all those defects that he had seen many times on those he worked on in the Ripamonti workshop in Mandello in Lario, assisted by Giorgio Ripamonti, the town blacksmith. The project, developed during the war years while he was serving as a seaplane engineer marshal of the Royal Navy, found support in close friendships with two pilots of the 260th Squadron, Giovanni Ravelli and Giorgio Parodi, to whom he showed his ideas, and the three decided who at the end of the conflict would have collaborated to carry out the project: Carlo Guzzi would have taken care of the construction, Giorgio Parodi, belonging to a wealthy family of Genoese shipowners, would have financed the undertaking, and Giovanni Ravelli, a valid motorcycle racer already known before the war , would have been the driver who would have promoted the motorcycle on the race grounds. Unfortunately Giovanni Ravelli died in an accident during a test flight on 11 August 1919: it was in his memory that the Eagle with spread wings was subsequently introduced as the Moto Guzzi trademark, the emblem of the Naval Aviation. The prototype, built in 1919 in the Ripamonti workshop in Mandello del Lario, with the approval (and economic funds) of Giorgio's father, Emanuele Vittorio Parodi, presented numerous practical, as well as rational, technical solutions, some deriving from the aeronautical sector. The prototype, despite having passed the tests brilliantly, turned out to be too mechanically complex, expensive for mass production and also too futuristic: thus the Normale, the first motorcycle produced by Moto Guzzi and put on sale in the first months of 1921 differed from the prototype in various details, including the ignition system (replaced with a single spark plug) and the distribution (replaced with one with two opposed valves). The name was also changed: the acronym G.P. it could easily be exchanged with the initials of Giorgio Parodi alone, and therefore the name Moto Guzzi was introduced. The engine, a 500 cm³ single-cylinder four-stroke (displacement then considered medium-small, but capable of offering considerable performance for market needs), was horizontal, facing forward, thus exposing the cylinder head - the hottest point of the engine - directly into the wind of the march; the bore/stroke ratio was 88 x 82 mm, therefore super square, a solution never adopted in the motorcycle field at the time, which allowed, in addition to the adoption of larger diameter valves (with therefore advantages for performance), the use of a shorter and less stressed connecting rod due to the lower speed of the latter. The distribution, with four parallel overhead valves controlled by an overhead camshaft in turn driven by a shaft and bevel gears, combined with the recall of the valves with needle springs and the double ignition controlled by a single Bosch magneto (which guaranteed excellent combustion of the mixture in such a large combustion chamber, given the super-square bore/stroke ratio), were applications of aeronautical origin, learned during service on the seaplanes of the Royal Navy during the war. To reduce vibrations and obtain greater robustness of the crank mechanism and crankcase, a large external flywheel was installed on the left side of the engine (which became the symbol of Guzzi and ironically called the "slicer"); the aluminum crankcase contained both the crankshaft and the gearbox, so as to use a single lubrication circuit and eliminate the primary chain, using instead a pair of helical tooth gears. The gearbox was thus in direct drive, resulting in the engine turning in reverse with respect to the wheels, a considerable advantage for lubrication, as the oil leaking from the connecting rod head was projected onto the upper wall of the cylinder, which by gravity fell onto the lower one, which would not have been possible with normal rotation, causing the oil to end up directly at the bottom and leaving the upper part dry. To improve the stability of the motorbike and the driving comfort, also taking advantage of the engine which was not very developed in height, a very low frame was created, with an under-barrel tank, with a continuous double cradle, shock-absorbed at the front with a parallelogram fork and rigid at the rear. The very low compression ratio, of 3.5:1, also limited by the quality of the fuels of the time, was still capable of developing around 12 HP and taking the motorcycle to 100 per hour.
