The Yamaha YD1 250 cc twin was a giant leap forward for the company. Yamaha studied the German Adler MB250 as also Honda did (they took the leading link front suspension). But Yamaha wanted more and the engineers got free hand from President Kawakami. Together with GK designers they created this motorcycle and only the crankcase construction remained as Adler influence. The machine measured 1935 mm long, wheelbase 1270 mm, weight 140 kg and the engine developed 14,5 hp @ 6.000 rpm. It had a 4-speed gearbox and tyres were 3.25 - 16, at that time a very popular dimension for this class of motorcycle. In July '57 a 260 cc version was added (tax-reason). On the bottom-r.h. picture you see President Kawakami trying out the first prototype of the YD1.

Yamaha YD1, Apr. '57