The YD-1, launched by Yamaha in 1957, was the company's first fully in-house-designed 250cc-class motorcycle with a twin-cylinder engine. With 247cc displacement, maximum output of 14.7ps and a retail price of ¥185,000, it featured a design focused on light handling and sporty performance.
Yamaha's YD-1, introduced in 1957, was the company's third model after the YA-1 and YC-1, and its first fully in-house-designed motorcycle in the 250cc class. Yamaha's designers reportedly described the project as having been entrusted with “a job of responsibility,” reflecting their strong commitment to developing original products.
The YD-1's chassis design became the starting point for the development of the first large-displacement motorcycle in Japan. Numerous updates aimed at improving performance were incorporated, including small-diameter 16-inch front and rear wheels, a telescopic front fork and a swingarm-type rear suspension. The fuel tank was designed with a tall profile, creating the distinctive style known as “Bunbuku Chagama.”
The engine was an air-cooled 2-stroke parallel twin with 247cc displacement, maximum output of 14.7ps／6000rpm and maximum torque of 1.9kgf・m／4000rpm. As an early twin-cylinder design, development of the split left-right crankshaft reportedly presented difficulties.
The YD-1's retail price at the time was ¥185,000. It marked a major turning point as Yamaha sought to transition to a sports-oriented motorcycle while balancing a larger body with practical utility.