the new four-cylinder was introduced in 1973, but the machine was unreliable, so that the three-cylinder machine was often used. initially, the four-cylinder had a single front disc and spoked wheels. a 3.00-18 front tire was used, and, depending on circuit, a 3.25, 3.50 or 3.75-18 rear tyre. it was a difficult year for mv agusta and especially so for giacomo agostini. they had attracted phil read as "second driver", but he did not accept a supporting role. moreover, the four-cylinder two-stroke yamaha tz 500 appeared, on which jarno saarinen won the first two gps. agostini still trusted the three-cylinder, but in the first race he was beaten by read on the four-cylinder. in the gp of germany, read won after saarinen, kanaya (both yamaha) and agostini had dropped out. after the fatal accident in monza, where saarinen and renzo pasolini died, the 500 cc race was cancelled and yamaha withdrew for the remainder of the season. as previously agreed, the top riders stayed away from the isle of man tt, meaning the next race would be in yugoslavia. however, due to a controversial decision by team leader magni, the mv drivers were not allowed to drive. he was not convinced of the safety of the track, which was approved by a delegation of four drivers, including agostini. in the tt of assen, agostini dropped out again and read won. agostini won in belgium and czechoslovakia, but read still had a comfortable lead in points and ago was behind kim newcombe and jack findlay in the rankings. read became the world champion at the grand prix of sweden. he had driven the new four-cylinder for most of the season. agostini was third in the world motorcycle championship.