Following the success of its 175cc single-cylinder racer and the derivative 250 version during the early and mid 1930s, the Benelli factory embarked on the creation of a new 250 racer for the 1938 season.
Devised by brothers Giuseppe and Giovanni Benelli, the new machine bore resemblance to its 250 predecessor, but it was pretty much an entirely new design. The engine was still a vertical DOHC single, but with a new 65x75mm bore and stroke, capacity was slightly increased from 246.7 to 248.8cc. The twin overhead cams were driven by a redesigned geartrain, which also drove the Marelli magneto and oil pump. The oil feed to the now fully enclosed valve gear was cast into the geartrain’s alloy cover, and the ’38 250 also featured a new, Benelli-designed 4-speed gearbox. A bigger 28mm Dell’Orto carburettor and a new long-length exhaust also contributed toward 26bhp at 8,400rpm – sufficient for a competitive 115mph top speed, although there wasn’t useful power below 6,000rpm.
The simple cradle frame and front girder forks remained relatively unsophisticated, but the new 250 did boast swinging arm rear suspension – a significant step forward from the previous model’s rigid rear end.
The 1938 European Championship season went well for Benelli. Although DKW eventually took the 250 title, the Pesaro firm’s machines took all three podium positions in the Italian 250 GP at Monza, a race run concurrently with the 350cc class. As a bonus, the first two 250 Benellis beat the 350 class winner Ted Mellors and his Velocette.
This Monza performance so impressed multiple GP winner Mellors, that he approached Benelli about securing a 250 for the following year’s Isle of Man Lightweight TT.
Briefly, Benelli lent him a 250 Bialbero, along with just one mechanic and a few spares, and this was sufficient for Mellors to be fastest in practice and secure both his and Benelli’s first TT win, beating formidable opposition from the DKW and Moto Guzzi factory teams and their supercharged machines.
Coincidentally, and unlike the earlier 1935-37 250 racer, the ’38 model was both a works machine and available to privateer riders, and the example offered for sale here (engine no. 200027) is one of those customer bikes. It is in restored condition throughout and comes with German historic vehicle documentation obtained in November 2002. Since then it has formed part of two private collections in Italy, the latter from 2011.
|Auction||The Carole Nash MCN London Motorcycle Show February 2016|
|Day of Auction||N/A|
|Registration Number||Not Road Registered|
|Model||250 S Bialbero|
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