mv agusta's famous racing machine, the three-cylinder or tre, had powered giacomo agostini to the world champion every year from 1966 to 1972. in the 1972 season, the tre was only just powerful enough to beat the newly created competition of two-stroke motorcycles from yamaha and suzuki. for the 1973 season, the existing 350 cc four-cylinder was bored to 433 cc, which could reach higher engine speeds than the three-cylinder. the new engine produced 88 bhp (65 kw) at 14,000 rpm.