In 1971 five
500 cc V-twins were built to compete in Italian championship and Grand Prix events. Ducati felt that this would demonstrate the bike before a large audience and gain publicity. If they won, that was a bonus.
Seeley Even before this, in late 1970, and despite Taglioni's opposition to the idea, Spairani wanted the frame for Ducati's racer to be built by
Colin Seeley, a well-known British specialist frame builder of the time. Seeley was asked to develop a racing frame similar to those he had built for
Matchless G50 engines. Ducati sent some prototype crankcases for Seeley to work from and the new Seeley frame was ready in February 1971. Meanwhile, in less than six months, Fabio Taglioni and his team had designed and built their own complete bike.
GP Bike technical details While the
750 cc and
500 cc racers were very similar, the 500 had a much shorter 58 mm
stroke, with the same 74 mm
bore as the 750. The 500 had the same bore and stroke as the later 500
Pantah. It had 10.5:1
compression and initially produced 61.2
bhp at 11,000 rpm. All Ducati's
500 cc GP engines used
desmodromic two-valve heads with an 80 degree included valve angle. They used remote float bowl
Dell'Orto 40 mm
carburettors, and had a six-speed
gearbox with a dry, multiplate clutch. Ignition was electronic, provided by nearby
Ducati Elettrotecnica, but was initially unreliable. Dual spark plugs were used, and the final ignition system used four coils, two on each side of the frame. In the beginning Taglioni's Ducati chassis was used. It had a single Lockheed front
disc brake and a twin leading shoe Fontana rear
drum brake. Dry weight was 135 kg (297 lb) and it had 18 inch rims front and rear with 3.00 and 3.25 wheel rims. The wheelbase was 1430mm (56.3 in). In June 1971, Phil Read tested the
500 cc bike with the Seeley frame, and pronounced it the better of the two. The frame was then fitted to Spaggiari's bike as well. It was raced in 1972 by Bruno Spaggiari, Ermanno Guliano and Phil Read. ==Production 750 GT==