The end of the 2006 MotoGP season also marked the last ever race for the 990cc prototypes, including Yamaha's YZR-M1, with new 800cc engine regulations being introduced for next season.
During the five-years that it raced, the M1 claimed 27 MotoGP victories - two with Max Biaggi (2002) and 25 with Valentino Rossi (2004-2006) - plus two riders' world championships, with Rossi in 2004 and 2005. The Rossi/Colin Edwards/M1 partnership also gave Yamaha the 2005 constructors' championship and the teams' title in both 2004 and 2005.
This year, Rossi came within five-points of his sixth consecutive world championship and, after the season-ending Valencian Grand Prix, YZR-M1 project leader Koichi Tsuji gave a technical presentation detailing the evolution of Yamaha's MotoGP machine during the 990cc period, from 2002 to 2006.
Quotes and diagrams from that presentation are shown here (click on pictures to enlarge), with part one detailing how the M1 has developed since 2002, while part two will concentrate specifically on the 2006 machine, which initially struggled with chatter before a storming fight back put Rossi in the championship lead heading to the Valencia season finale...
"The YZR-M1 has been developed continuously around three main themes; chassis, engine and engine management system," began Tsuji. "For the chassis, we continued Yamaha's tradition of good handling characteristics even further by maximising agility.
"We always want more power from the engine, but at the same time we spent a lot of time trying to achieve a balance between power and drivability, by having a rideable torque character. For the engine control system, so called EMS [engine management system], we always try to create a direct natural feeling.
"This chart [top picture, 'YZR-M1 Concept'] shows the main history of the YZR-M1. In 2002, the bike was based on a 500cc chassis with a four-stroke engine," continued Tsuji. "2003 saw a further evolution, the biggest change being the use of fuel injection instead of carburetor, while the engine brake control system was changed to the ICS [Idle Control System].
"Then in 2004 we enjoyed the arrival of Valentino. Sure his great talent gave Yamaha the world championship, but the engine also saw big changes and progress. We introduced a four valve [instead of five valve] cylinder head and an un-even [big bang] firing order. This made a huge difference in the performance of the YZR-M1.
"For the next two years, we continued to develop the 2004 machine and for the future after 2006 we will continue to develop this very successful concept."