Ing. Savelli designed a new four-cylinder GP 250 which appeared on the track Imola in 1962 and which was developed over the following seasons into Kel Carruthers' 1969 title winning machine. The 250/4 campaigned in the early 1970s by Saarinen and and Villa was a completely different design by Savelli's successor Piero Prampolini.
The 1964 model was ridden to victory by Tarquinio Provini in the 1964 Spanish GP, and he took the 1965 and 1966 Italian Senior Championship titles along with a victory at the 1965 Italian Grand Prix aboard the GP 250.
Provini's '64 model differed in a number of aspects from that which was raced by Grassetti during the 1962-63 season. The 2 valves per head were set at 90° (later to 63°) and a 7 speed gearbox was commonly used (although 5 to 8 speeds could be fitted). The prototype had a dry sump with the oil tank fitted under the seat but this soon was changed to a bolt on sump that held two litres.
The battery and four-coil ignition was replaced initially by a Lucas magneto, and then in late 1964 by one from a four-cylinder Mercury outboard engine that could better handle the high rpm. The '62 prototype used four 20mm carburettors but later versions used either 24mm or 22mm, depending on whether the track required higher power or greater torque. Power of the '62 version was 36.5 h.p. at 12,500 rpm but by '64 it was up to 45 h.p. at 14,000 rpm; by 1965 it was developing 48 h.p at 14,500rpm, and then 50 h.p. at 15,000 rpm from '66 onwards. The later 16 valve motor made some 55 h.p at 16,000 rpm the power band was narrow. A higher torque 12-valve engine (twin inlet/single exhaust) was also experimented with. The 1962 frame was replaced by a more modern chassis in '64 - still fitted with Oldani drum brakes. Benelli was the first factory GP team to use disc brakes, in 1965.
Sources: Phil Aynsley, H&H Classic Auctions, et al.
