The YDS1 arrived in July 1959. In 1957 the second Asama Volcano race was held on the newly opened Asama Automotive Testing Ground and this was the scene of a direct confrontation between the giant Honda and the upcoming Yamaha. Yamaha defeated Honda convincingly in both the 125 cc class and the 250 cc class. The 250 cc machine was Yamaha's YD-A/B works racer. 5 of these machines, further developed, were later sent to the Catalina G.P. in the USA in 1958, where Fumio Ito scored a sixth place. While transforming the YD2 into a more sedate roadster, Yamaha catered for the sporting set by introducing an entirely new sporting model which was a derivative of the Asama-Catalina racer, This was the YDS1, initially introduced as 250S, featuring a new tubular duplex cradle frame. it was a purposeful machine with such mecahnical elements as carburetors, battery, electrical equipment all exposed.

Overall length was1990 mm, wheelbase 1285 mm, weight 151 kg, with 3.00-18 tyres. The 2-stroke parallel twin had the same bore/stroke of 56 x 50 mm as the Asama B type racer for a total of 246 cc capacity, from which it produced 18 hp at 7.500 rpm and it was mated to the first Japanese 5-speed gearbox. Yamaha separated sports from utility, but they intended the YDS1 to be a versatile sportster and prepared conversion kits for dirt racing (like Asama and Catalina) and enduro type competition. An interesting side-note is that the company displayed a promising 125 cc prototype sportsmodel, called Sports 125, at the 1959 Tokyo Motor Show, featuring a six speed gearbox. But this machine did not go into production. The YDS1 and its 260 cc sister model YE1 were commercially successful, and led the the later RD series of sports roadsters.