The new single-shock design by Yamaha was called the Monoshock and was introduced in 1974, but not sold until 1975. The YZ250/360B’s were destined to change the entire way motocross motorcycles were designed and built.

The new Yamaha models were sold and marketed to expert only riders. One thousand 250’s were built and far less 360’s ever hit the motocross track. The motor, brakes, and front end were similar to the YZ-A models, featuring drilled and lightened hardware, magnesium, and just the bare essentials. The monoshock frame was much heavier than the A models, but the handling was superb and really enabled the expert rider to put the 360’s power on the ground.

Hakan Andersson was the first rider to race the 360B in a GP motocross event. The event was the 3rd race of 1973 held in Belgium and Hakan won convincingly. He was soon on a roll with an unbroken string of 11 wins out of 22 GP starts and went on to win the 500cc World Championship in 1973.