Yamaha loves big bikes. Clearly, there’s a connection between the people at Yamaha and the idea of large displacement motocross bikes, going all the way back to the days when 360cc was considered large and a 500 was outrageous. Through most of the ’70s, Yamaha was the only Japanese maker to even offer an Open-class MX bike. But the connection goes even farther back. You have to go all the way back to the first production motocross bikes from Japan. For Yamaha, that goes back to 1969. The 250cc DT1MX and the 360cc RT1MX were official models that year. They were based on the enduro bikes, but came stripped down for racing and had Yamaha’s GYT kit installed at the factory level. Those first bikes were the raw materials used for racing efforts in Europe and in the United States. Overseas, Torsten Hallman was the focus of a development program that used the World Championship GPs as a test bed. Over here, Gary and DeWayne Jones were the riders, and their father Don Jones was the engineer. Both camps sent their reinvented race bikes to Japan, and what came back in 1973 were all-new, works-level bikes that were sold to the public. That was the start of the YZ line.