Most riders considered four-stroke engine technology to be largely utilitarian and uncompetitive, relegated solely for trail riding.

[5] Yamaha engineer Yoshiharu Nakayama first came up with the idea of creating the first competitive four-stroke race motocross bike.

It solved the power dilemma by borrowing superbike technology and giving the YZ a five-valve head, liquid cooling and a 12.5-1 compression ratio.

In 1997, Yamaha rocked the motocross world with the introduction of the YZ400M prototype, a concept motorcycle which borrowed much technology from road racing.

The bike had an 11,600 rpm redline[8][better source needed] power and torque close to its 250 cc two-stroke rivals.

[4] The crankshaft was also reshaped and the whole assembly was redesigned for quicker throttle response and, Yamaha claimed, "less high-end horsepower loss."

The suspension also received a bit of an overhaul with the goal being reduced weight and smoother action throughout the stroke.

[10] Motorcycle.com says that "The gas tank is reasonably thin and allows good forward and backward movement while providing something nicely shaped to hold onto with your knees.

The foot pegs are well-made units with a wide platform and sit in a position that keeps them from dragging in ruts without cramping a rider's legs."

In 2002 Yamaha remapped the digital CD ignition system which delivers a more precise spark and optimal timing for faster, stronger response during hard acceleration, and less kickback during starting.

Also an all-new swing-arm which is lighter and stronger for reduced weight, greater rigidity and more compliant rear suspension action.

The 2005 YZ450F was the first YZ450F to feature KYB twin chamber cartridge forks.The YZ450F received a major update in 2006, with over 300 parts changed and improved.

The engine cylinder is rearward slanted, the crank rod angle has been changed to provide a more complete combustion, the 5-valve head is now a 4-valve head, the gas tank is located under the seat, the exhaust pipe exits the rear of the cylinder, and the air intake is now in the front of the bike.