The KX125 used a new rotary-valve two-stroke engine evolved from the engineering lessons learned from the high-output 1970 100 Centurion G31M dirt racer. Weighing 199 pounds, with its electrofusion-coated cylinder and six-speed gearbox, the 1974 KX125 immediately became a threat to win any 125 motocross race.
The KX250 anchored Kawasaki's new MX lineup with explosive two-stroke power, – along with such innovations as fade-resistant Hammerhead shocks. Dent-resistant plastic fenders kept weight to 214 pounds.
The range-topping KX450 delivered heroic power that only top riders could fully utilize—among them, 1974 AMA 500 Motocross champion Jimmy Weinert. A plastic fuel tank and fenders helped pare weight to just 220 pounds, making the KX450 a motocross missile.