From the mid-1970s through to 2001, the top class of Grand Prix racing allowed 500cc displacement regardless of whether the engine was a two-stroke or a four-stroke. Because two-stroke engines fire on every crank revolution and four-strokes only every second, a same-displacement two-stroke produced considerably more power in this context, and the four-stroke was consequently extinct at the front of the field. Honda's NR500 project in the late 1970s and early 1980s attempted to resurrect four-stroke competitiveness but failed entirely; by 1983 even Honda was winning with a two-stroke 500.
As engine technology advanced through the 1990s, lap speeds escalated to levels that the FIM and Dorna regarded as a safety and spectacle problem. The major Japanese manufacturers were also keen to compete with technology that bore a direct relationship to their road-going products. Regulations were drafted that would allow four-stroke engines into the premier class with a substantially enlarged displacement ceiling so that they could be competitive against the existing two-strokes, while retaining two-strokes as a transitional option for independent teams unable to immediately fund new machinery.
The new MotoGP regulations permitted two-stroke engines of up to 500cc or four-stroke engines of up to 990cc to compete in the same championship. Four factory teams — Repsol Honda, Marlboro Yamaha, Suzuki, and Aprilia — entered with the new four-stroke machines from the start of the season. All satellite teams initially ran the existing 500cc two-stroke bikes. The difference in performance was decisive and immediate.
Honda's new four-stroke machine, the RC211V, was a 990cc V5 configuration. Valentino Rossi, riding the RC211V, won the very first race of the new era at Suzuka in wet conditions, taking an all-four-stroke podium alongside a Suzuki and a Yamaha. Over the course of the season Rossi won 11 races and accumulated 355 points to claim his second consecutive premier class championship with four races still remaining. His teammate Tohru Ukawa took a further victory. Max Biaggi, on the four-stroke Yamaha YZR-M1, added another win at Brno.
Two-stroke machines recorded five podium finishes across the entire season but took no victories. Kawasaki returned to the premier class as wildcard entrants in the final four rounds, running a four-stroke ZX-RR as preparation for their full 2003 entry. Honda progressively expanded the four-stroke presence mid-season by supplying the RC211V to the Gresini satellite team from the Czech Republic Grand Prix onward.
The performance gap between the 990cc four-strokes and the 500cc two-strokes was so large that independent teams quickly sought access to customer four-stroke machinery. By the 2003 season no two-stroke machines remained on the MotoGP grid. The last two-stroke engine was started in MotoGP competition at the 2003 Czech Grand Prix, and the class was from that point forward a solely four-stroke formula.
The 125cc and 250cc classes retained their two-stroke machinery until the successive introductions of the Moto3 and Moto2 classes in 2012 and 2010 respectively brought four-strokes to all three tiers of the Grand Prix pyramid.
The 2002 transition fundamentally reshaped the sport and its commercial relationships. With 990cc four-stroke prototypes, development costs escalated dramatically but so did manufacturer ambition. Ducati debuted as a Grand Prix constructor in 2003 on the back of the new formula, and the era produced some of the most powerful and technically complex racing motorcycles ever built, eventually reaching the point where the championship capped displacement at 800cc for 2007 specifically because the 990cc machines had grown too fast. The rebranding of the premier class as MotoGP rather than the 500cc class simultaneously signalled a new commercial identity for the championship, which Dorna exploited to grow global audiences through the 2000s.