Dario Ambrosini won the Benelli 250 Bialbero

Benelli 250 Bialbero

With Phil Aynsley

The bike you see here is the Benelli 250 Bialbero that Dario Ambrosini rode to win the 250cc world championship in 1950.

I photographed it at the Morbidelli Museum in 2011 but it sold at auction in 2020 for £138,000, setting a new record for the brand (this record rose to £149,500 a few minutes later for a 1964 Provini 250/4!).

The Benelli 250 single was the follow-up to the company’s successful 175 cc racer and was launched in 1934. It deliberately retained most of the 175’s features following the motto “If it ain’t broke, don’t fix it”.

The only notable change was the switch to a long-stroke design. Twin overhead camshafts were driven by a series of gears and a separate four-speed gearbox was used.

The oil tank is located behind the dry-sump engine. The 250 set the World Speed ​​Record in its class in 1934 with a speed of 181.81 km/h but its GP career was not as successful as the Moto Guzzis that dominated the class.

By 1936, the 65 x 75 mm bore was revised and factory rider Ted Mellors won the 1939 IoM Lightweight TT. Suspension was monoshock and piston rear.

A turbocharged version was designed to compete with the Guzzi and DKW lines but war broke out before it could be built.

When racing resumed in 1948, the old 250 was back on track in the hands of Ambrosini and won the championship two years later.

Power output is 27 horsepower at 9500 rpm, weight is 115 kg and maximum speed is 180 km/h.

Benelli 250 Bialbero Specifications