In September 1964, famed Honda engineer Michihiko Aika and rider Jim Redman climbed aboard a BOAC VC10 at Tokyo’s Haneda airport, bound for Monza, via Hong Kong, Calcutta, Karachi and Rome. Sitting next to them was their new motorcycle, laid across three passenger seats and hidden beneath a blanket. The decision to race the bike at the season-ending Italian Grand Prix had been last minute, too late to freight it to Italy.

The machine was Honda’s RC165, a six-cylinder 250cc four-stroke created to defeat Yamaha’s twin-cylinder RD56 two-stroke, which had proved too much for Honda’s four-cylinder RC164.

The RC165 was Honda’s most famous weapon during its 1960s war with the burgeoning two-stroke force, led by Yamaha and Suzuki. The 250 six and its lesser-known stablemates the RC148 125cc five and RC115 50cc twin were also important symbols of Japan’s new industrial might and perfect examples of the nation’s fascinating technology of miniaturisation. The 250 six had a bore and stroke of 39 x 34.8mm, while the 125 five and the 50 twin measured 34 x 27.8mm. Pistons like espresso cups.

The engineering concept behind these shrieking engines was straightforward: a two-stroke fires twice as often as a four-stroke does, therefore the four-stroke must rev twice as high. The 250 six revved to 18,000rpm, the 125 and 50 went to 21,000, compared to Yamaha’s 11,000rpm RD56.

Remarkably, these engines, and Honda’s first Formula 1 engine, the RA270, were mostly designed by one man, the brilliant Shoichiro Irimajiri, who was only 24 in 1964.

Irimajiri had wanted to design jets, but Japan was banned from engaging in such activities after the Second World War, so he joined Honda instead.

Honda itself was emblematic of Japan’s new role in the world. Metallurgist Soichiro Honda had established his company in 1948, by buying a job lot of Second World War army radio generators and installing them in bicycles to create low-cost powered transport. By 1965 Honda was the world’s biggest motorcycle manufacturer, producing 1.25 million units annually.

Honda’s stunning growth was part of a greater Japanese economic boom that had been largely precipitated by the Korean and Vietnam wars, for which the US needed a supply and repair base close to these new theatres of war. During the first 18 months of the Korean conflict billions of dollars flowed into the Japanese economy, the Tokyo stock market leapt 80 per cent and numerous US-Japan licensing agreements were signed. Irimajiri was one of many Japanese engineers who took advantage of this new relationship between his country and the USA.

“When we had trouble with materials, we went to General Electric or Pratt and Whitney in the USA,” he recalls. “They asked us, ‘what problems do you have?’ We explained, and they introduced us to a very special steel, a new material they were using for turbine shafts. In those days American companies were kind to us; they showed us everything so we could overcome these problems. We took samples home, went to Daido Steel or Nippon Special Steel, who analysed it and then made the same for us.”

With his innate genius and imported knowhow, Irimajiri revolutionised four-stroke technology. His engines made up to 280 horsepower per litre, about the same specific power output of a 2019 MotoGP bike; although modern grand prix engines are restricted in bore size, specifically to rule out any Irimajiri-style flights of fancy.