The YD frame as modified for the 1958 Catalina GP with additional footpeg mountings. It can clearly be seen that the subsequent racing machines followed this original design before Yamaha utilised the Showa influenced disk valve engines to produce the RD56 in 1963, although this basic design layout was to stay in Yamaha service on their production TD1 models until TD1C was replaced in 1969. Drawing by Chip Hellie.

It did not take Yamaha very long to develop their early racing two strokes into World beaters. They began by testing themselves against foreign machines in the USA; a bold move, as it was the 1st time a Japanese manufacturer had competed outside of Japan. They first entered the Catalina GP in 1958, which was a circuit comprising of mostly off-road with some tarmac surface. 3 years later in 1961 they returned to compete in the US Grand Prix at Daytona with full road race machinery (RR 250's), shortly followed by tackling the Isle of Man TT and World Championship Grand Prix's (RD48 & RA41) with some good finishes achieved, including Ito finishing 6th behind Honda's domination at the TT as well as several wins in the non-World Championship events such as the Singapore GP. 
1962 was a quiet year for Yamaha, with some major development of the race bikes undertaken as well as finding and training new riders. This proved successful with the new TD1 racing model taking the honors at the All-Japan GP at Suzuka in both the Novice and 350cc classes.
Early in 1963 Yamaha won in both the 250cc class (Fumio Ito) and the open class (Don Vesco) at Daytona on the new RD56 machine. Then the elusive first World GP win came for Fumio Ito at the Belgian GP, with Sunako gaining 2nd place.  At the end of 1963 Yamaha drafted in Phil Read for the following 1964 season. Phil won the 250cc World Championship, the first in a long line....