Moto Guzzi’s 1954 in-line 500/4 Racer

With Phil Aynsley

In a recent column I looked at Moto Guzzi’s eye-catching first attempt at a four-cylinder GP motorcycle (Link). In this column we look at its second attempt.

PA Moto Guzzi four cylinder racer
Here’s a look at Moto Guzzi’s second attempt at a four-cylinder racer

The final race of the 1952 season, the Italian GP, was the venue for its debut. The design had been outsourced to Carlo Gianini (who was responsible for the original OPRA motor that eventually became the supercharged Rondine 500/4).

PA Moto Guzzi four cylinder racer
Carlo Gianini was the designer

Gianini came up with an unusual longitudinal in-line four motor that was initially fitted with a mechanical/pneumatic fuel injection system. The DOHC heads incorporated valves that closed directly onto the heads, without any inserts. Final drive was by a shaft.

PA Moto Guzzi four cylinder racer
The longitudinal in-line four motor that was initially fitted with a mechanical/pneumatic fuel injection system

While fast the bike suffered from being overly complex, having a high centre of gravity and a difficult gear change action due to the shaft drive.

PA Moto Guzzi four cylinder racer
A high centre of gravity did not benefit this racer on the track

The multi-plate clutch also proved to be too small but that wasn’t able to be corrected without entailing a complete redesign of the rear of the motor.

PA Moto Guzzi four cylinder racer
Eye catching four-into-four exhausts look the business

Carburettors replaced the injection for 1954 as well as a dustbin fairing that incorporated pannier fuel tanks. This bike is fitted with the original fairing however.

PA Moto Guzzi four cylinder racer
Carbs were added to replace the injection system in 1954

The riders didn’t like the bike and it only achieved two victories, both in non-championship races. The design was shelved at the end of the 1954 season when the V-8 took over 500cc duties in 1955.

PA Moto Guzzi four cylinder racer
A shaft final drive also made for difficult gear changes

Power for the Moto Guzzi 500/4 Racer was 55hp at 9000rpm, while weight just 145 kg. A top speed of 230 km/h was possible.

PA Moto Guzzi four cylinder racer
The 1952 Moto Guzzi 500/4

PA Moto Guzzi four cylinder racer
1952 Moto Guzzi 500/4

PA Moto Guzzi four cylinder racer
1952 Moto Guzzi 500/4

PA Moto Guzzi four cylinder racer
1952 Moto Guzzi 500/4

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Neil C. Leach, Jr.
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Mr. Aynsley, what was it about the shaft drive that negatively affected gear changes? Thank you.