Back When: YZR M1 2004 – Rossi’s first Yamaha

motogp.com takes a look through history with ‘Back When’, exploring some of the most important races, bikes and riders throughout history.

Honda and Yamaha’s battle had waged for years both on and off the track. With the 2002 rule changes and the introduction of the MotoGP™ class, the four stroke engines presented their rivalry with a new dimension. New regulations meant more development, racing technology again testing and experimenting for future consumer products.

It was for this reason that Yamaha adopted a more conventional four-cylinder engine layout as opposed to the exotic V5 of their rivals Honda. From this point on the Yamaha became known as the ‘YZR M1,’ the Iwata brand looking for success in the new racing era.

The arrival of Valentino Rossi in the official team at the end of the 2003 season marked a distinct shift with the Yamaha. His move changed the expectations of many and saw a complete revolution within Yamaha’s racing department, accelerating the development process of the M1 to turn it into Rossi’s bike, a true championship weapon.

Within the framework of the inline four a number of different crankshaft settings were tested in the pursuit of power and make it as useable by the rider as possible. Four and five valves per cylinder were also tested with the same end goal, Yamaha eventually settling on four valves. Electronic carburettors had already been rejected during the 2003 season. The cylinders were inclined along the lines of the Yamaha R1, which allowed the frame, a classic twin beam aluminium design, to envelope the engine more and improve overall aerodynamics.

In the 2004 version of the Yamaha M1, the engine mounting spars at the front of the bike were longer than that of its predecessor as Yamaha looked for great rigidity. The centre of gravity was also lowered to improve traction, all MotoGP™ bikes and riders always hunting for more traction.

The results of all this work was a leap forward in the competitiveness of the bike, confirmed by the victory of Valentino Rossi in the first GP of the season in South Africa. Rossi took the title on his first attempt with Yamaha. It was the start of a relationship that would bring a number of great moments for the union of the Italian rider and Japanese brand in the following years.

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