The sensational 250cc Benelli supercharged four with town arms of Milan on the tank. "In the 250cc class, Benelli had enjoyed a successful 1939 season with the normally aspirated single which had propelled Ted Mellors to a rain-lashed TT victory. But in a determined attempt to stay on top of the quarter-liter pile, the Pesaro concern unveiled a new model at the Milan Show late in 1939.
"The sensational Benelli, boasting four cylinders, relied heavily on the single for cycle parts, merely transplating the same elementary frame, girder front forks, plunger rear suspension, 2.75 by 21 inch tyres, tank and so on. But the engine was a revelation. Each cylinder was of 42mm bore by 45mm stroke for a total capacity of 249cc. In the mode made fashionable by the 500cc Gilera, the four cylinders were mounted across the frame but inclined only by 15 degrees. The two valves per cylinder were governed by a dohc assembly with a T-shaped cascade of gears on the right hand side of the engine. An extension ran to the front of the engine to drive the magneto. Water cooling was employed with the radiator mounted on the front down tube, while the oil tank was beneath the saddle.
"The gear driven blower was a Cozette vane type, mounted above the four-speed gearbox. The supercharger employed one carburettor and a compensating lung with generous circular finning. The four exhaust pipes merged into two on either side.
"This fearsome power plant supposedly produced an undreamt of 52bhp at 10,000 rpm, producing a purported top speed of 145mph in GP trim and 155mph in streamlined guise for record attempts.
"Regrettably, the war started before the machine had the opportunity to show its pace on the racetrack. An example survived the devastation inflicted on the Pesaro factory by retreating German armies but, thanks to the FIM ban on supercharging, it was destined never to turn a wheel in anger. Today only an engine remains intact."
--Classic Racer, Winter 1987
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