A young man arrived and knocked on the tightly shut door to the prototyping workshop at Nippon Gakki (today’s Yamaha Corporation) and entered with a bowed head while apologizing for the disturbance. The engineers bent over their drawing boards ignored him—he wouldn’t be there if he hadn’t been entrusted with an accordingly important task—and they carried on intently sketching a variety of small parts. The young man would later write how he was awestruck by the focus and intensity with which they worked.

The design and development of the YA-1 was carried out largely in secret by a very select number of people; three engineers designed the engine, three handled the chassis, and one was in charge of the electrical system. With the unwavering dedication they showed to the tasks at hand, these engineers would later be called the Seven Samurai of motorcycles, for they reminded others of the titular characters in Akira Kurosawa’s movie masterpiece.

The first thing the team did was disassemble the DKW RT125 they had for a reference model. Each and every part was carefully measured and drawn, and this required them to fashion their own measurement jigs. Unsure of the frame’s internal structure, they loaded it up and transported it to a distant university that had an X-ray so they could learn its secrets. What the young man saw that day—the group of seven facing their drafting boards with brows furrowed in intense focus—was a comparatively small part of the enormous workload they were shouldering in this all-new challenge.

In developing the YA-1, President Genichi Kawakami strictly ordered that it be an exact copy of the RT125 and there were two reasons for this. First, by faithfully reproducing such a world-famous motorcycle, the engineers would undoubtedly acquire much knowledge and technological insight. Second, even though they would be the last domestic manufacturer to start building motorcycles, President Kawakami believed that creating a perfect reproduction of the RT125 would give them an edge on the competition.

But on the other hand, the engineers could not hide their own ambition to make the YA-1 even better than the original. Some of the standout changes they made were upgrading the original 3-speed transmission to a 4-speed to make their bike more suited to Japan’s hilly terrain, and modifying the starter to a primary kick type for greater ease of operation. The engineers also designed a new mechanical layout that positioned the gearshifter and kick pedal on the same axis. These were some of the many improvements, both large and small, that were made to the original design.

In the prototyping workshop set up within Nippon Gakki’s machine tool factory, preparations for designing the engine were complete in March 1954 and chassis design began three months later. From there, the Seven Samurai worked with ferocious intensity to complete the first prototype and were able to narrowly meet the original August 31 deadline. This first hand-assembled prototype then embarked on and completed a grueling 10,000 km durability test by riding repeated 65 km laps around Lake Hamana.

One year later, the engineers and President Kawakami were standing at the summit of Mt. Norikura 3,026 meters up. By then, the YA-1 was already on the market and the motorcycle division had been split off from Nippon Gakki to establish Yamaha Motor Co., Ltd. as an independent business entity. President Kawakami accompanied his engineers on this test ride up the mountain, all of them riding YA-1s through the steep valleys and treacherous fields of sharp volcanic rocks on a journey to the top that tested their mental fortitude.

Even after completing all the technical drawings and the prototype itself, the engineers still couldn’t afford to take a break; they now had to design the jigs and tooling needed to actually produce the YA-1 as well as share duties in overseeing the assembly of the bike at the factory. However, one account of the team’s test ride on Mt. Norikura’s demanding slopes that day includes the following vignette: “[Along] the way, we ate some Shinshu soba noodles at the remains of Komoro Castle in Nagano Prefecture, and everybody who was there remembers how incredibly delicious those noodles were.” Some believe that this meal during the test was not just to fill hungry bellies but also one way President Kawakami expressed his appreciation for all the hard work his Seven Samurai had done.