The fuel-injected YZ450F will enters its third season as part of the AMA Supercross series (also an FIM World Championship) in 2012 and will again count on the immense talents of James Stewart as well as Davi Millsaps as part of the JGRMX crew for the seventeen round contest.

With the introduction of the four-stroke YZM400F factory prototype in 1997 Yamaha changed off-road motorcycle sport as few other manufacturers have ever achieved before. The YZM400F brought four-stroke power and traction with an agile two-stroke type of chassis to the race track, a concept that in the end proved to be more competitive than the commonly used two-stroke machines of that era. The initial stones in the YZ ‘wall’ of supremacy were laid in 1998 when Doug Henry took the YZ400F to a thrilling debut in the AMA-MX championship, winning five nationals on the way to the crown. He also gained four podiums within the Supercross campaign of that year.

In 1999, Andrea Bartolini won the machine's first Rider’s World Championship in the 500cc class with the production based YZ400FM and ever since that time Yamaha have led the four-stroke revolution. The bike has formed the basis of winning technology in MXGP, MX1, MX3 and AMA Supercross and AMA Nationals since the turn of the century; most notably through 426cc and onto 450cc for the MX1 class from the beginning of 2004. Stefan Everts won the 500cc world title in 2001, 2002 and MXGP crown with the 450cc model in 2003. He then added crowns in 2004, 2005 and 2006 before retiring triumphant.

In 2008 innovations of the production YZ450F involved a new aluminium frame with altered geometry, making the base for racing machinery extremely competitive straight from the crate.

For 2009, on the race-bike, an altered swing-arm and linkage system helped lighten and add precision to the handling while the rear hub also carried less weight. The 2009 YZ450FM as used in MX-GP was a further, refined development of the motorcycle that propelled the legendary Everts to his 2006 world title, winning fourteen from fifteen Grand Prix. Josh Coppins’ took the machine to within one race of the 2007 MX1 championship (taking five wins on the way) and Grant Langston became the last rider to earn the AMA Pro National 450 Motocross Championship for Yamaha.

Philippaerts claimed the MX1 title in only his second season in the premier category during 2008, continuing a fantastic run of results for Yamaha's strong four-stroke technology. In 2009 Antonio Cairoli used a De Carli-tuned version of the YZ450F to win the title at his first attempt.

2010 saw Yamaha dazzle the market and race paddocks again with a brand new YZ450F. The rear slating and re-positioned fuel-injected engine unit benefitted from a new configuration with innovative displacements of the airbox and exhausts. Housed within a chassis that helped lower and further centralise the riding sensation the motorcycle was feted by the world’s press. James Stewart won five rounds of the 2011 AMA Supercross series – dubbed the best season ever – and takes the 2012 version of the machine into battle during the early stages of this year.