The Yamaha YZR-M1 is an inline-four motorcycle specifically developed by Yamaha Motor Company to race in the current MotoGP series. It succeeded the YZR500 by the 2002 season and was originally developed with a engine. Since then, the YZR-M1 has been continuously developed into several iterations through the 990cc, 800cc and 1000cc eras of Grand Prix Motorcycle Racing. 2002–2003 2002 was the first season which allowed 990 cc 4-strokes to be raced alongside 500 cc 2-strokes. In a change from their V-4 YZR500, Yamaha designed the YZR-M1 (for "Mission One") with an inline-4 engine because it was the format considered to have the best mutual balance with the frame. Also, Yamaha wanted to preserve the superior handling of the YZR500, so the M1's engine was designed to fit in a chassis developed around the basic structure of the YZR500. The M1 was outfitted with an electronic engine management system that controlled the engine braking endemic to 4-strokes. The new engine had 5 valves per cylinder, was fed by carburetors and began with a displacement of 942 cc; in the second half of the season it progressed up to the full 990 cc regulation limit. The frame design also evolved during the season, with adjustment of the engine mounting position and change in the fuel tank shape. The M1 was test-ridden and developed by Max Biaggi, John Kocinski, Norihiko Fujiwara and Kyoji Namba throughout 2001. It was raced in the 2002 season by Biaggi and Carlos Checa on the factory team, and towards the end of the season M1s were also provided to Norifumi Abe, Olivier Jacque and Shinya Nakano. Biaggi achieved two wins and placed second in the final standings as did Yamaha in the manufacturers' championship. In 2003, the engine went from carburetion to fuel injection, and the engine brake control system was replaced with an Idle Control System that automatically adjusted the throttle valve opening on two of the four cylinders to improve stability and handling during deceleration. M1 riders were Checa, Alex Barros, Olivier Jacque, Marco Melandri, Shinya Nakano and Norifumi Abe, and there were no wins and Yamaha came in third in the manufacturers' championship. 2004/2005 Valentino Rossi signed a two-year contract with Yamaha, reportedly worth in excess of US$6 million per season, in a move that was described by the press as "biting off more than he could chew". It was widely felt not only