A new era began in 1971 with the development of twin-cylinder two-stroke racers of 250cc and 350cc capacity, designed at Aermacchi by their chief engineer, Ing. William Soncini. The first 250cc racer was very fast, with 46hp at 11,000rpm, and weighed only 250lbs. After Harley-Davidson acquired 100% of Aermacchi in 1972, they funded further racing development at the Aermacchi factory, and the racers were branded with Harley-Davidson on their fuel tanks. These two-stroke twins provided Harley-Davidson with their only Grand Prix wins, and four World Championships: 250cc World Championship in 1974, '75, and '76, and the 350cc World Championship in 1976, all under rider Walter Villa.Walker, Mick: Mick Walker's Italian Classic Gallery - the Racing Bikes. 1991, Haynes.
