Moto Guzzi supercharged OHV 500cc four
With Phil Aynsley
This is one of those bikes that stops you in your tracks when you first see it!
In 1931 Moto Guzzi decided they needed a new design to be competitive with the supercharged four-cylinder CNA (that went on to become the Gilera Rondine). This amazing looking beast was the result.
The OHV, four-cylinder motor featured a Cozette supercharger fed by a single 28.5mm carburettor. A high pressure intake plenum was placed above the nearly horizontal cylinders. Two camshafts drove the external pushrods and twin magnetos were also used.
The three-speed gearbox was operated by a hand change. The two valves per cylinder had a 70º included angle. With the supercharger operating at 0.75 bar output was 45hp at 8000rpm.
Unfortunately the weight of 165kg, together with the high power (for the time!) overwhelmed the frame and rather small brakes, thus the 500/4 only made a single race appearance, at Monza in 1931, where all three bikes entered failed to finish (a fourth bike was also built).
While a failure as a race bike the design was used as the basis for the 500 triple touring road bike introduced in 1932.
