In 1956, Messrs. Honda and Fujisawa traveled to Europe together. On the surface, their purpose was to make an observation trip, but actually the two had an idea for a completely new product, and they took this trip in order to substantiate it.
The Cub F-Type had gone out of production. The type of bike known as a "Mopet" in Japan (derived from the European motorbike with pedals known as a Moped) was growing in popularity there, replacing the auxiliary engine for bicycles.
A brochure dating from the time the Super Cub went on sale. The lettering in the word "Super" was clearly designed in line with the Cub F-Types logo. The people involved at the time say it was almost totally hand-crafted. (Brochure courtesy of Jozaburo Kimura)
Every time Honda looked at the mopeds running on the streets in Europe, he would ask Fujisawa:
"That kind there? Or this kind here?"
Fujisawa would just shake his head.
As soon as they had returned to Japan, a meeting of the executive board was held, after which the two men conveyed the board's instructions for development of a new product. The vehicle that Mr. Honda had imagined was explained to the engineering design staff. Yoshiro Harada, then Head of the Frame Engineering Design Section, was made the leader of this project. He remembers:
"The principal people were told to get together, and the Old Man talked about the idea he had in his mind. It was close to a Moped, but it would be different, that much came across. He had come back with about five sample bikes he had bought over there. There were an NSU from Germany, a Zundapp, a Puch from Austria, and so on. The Old Man was always thinking about mass producibility, and this time we all figured out that he had mass production on his mind more than ever. Actually, the Old Man had us make two prototypes even before he went to Europe. One of them was just wild, with a body made entirely of cast aluminum. It may have been suited to mass production, but the weight made it unworkable. We gave up on that one pretty quickly. At that point, the Old Man himself hadn't formed a clear image of what he wanted yet."
"As we went on, it gradually became more concrete," Harada recalled. "The Old Man would get to the Engineering Design Room early in the morning and call out, 'Hey, last night I thought of this,' and everyone in the room would come over to see what was up. Then he would get even more excited and start spluttering as he explained. After a while he would get impatient, and then he would squat down and start sketching his idea on the floor with chalk. While he was drawing, he would be thinking ahead, so he'd use his hand to rub out what he had drawn and start sketching again. His audience would keep on increasing. The Old Man would be in the center of this circle of people, just like a sidewalk performer," he continued, laughing. "The employees who surrounded him, though, would all be quivering with tension as they listened to the Old Man. 'The engine will be a 4-stroke!' and, of course, this had long since been decided. That wasn't Mr. Fujisawa's request. The Old Man had come to really hate 2-stroke engines then. He just despised them. In the New Year season of 1957, we started development, beginning with the engine."
Daiji Hoshino was in charge of the engine. Honda had specified during a board meeting that he should develop the new engine.
He says: "I had joined Honda in 1951, and was immediately put to work on the Cub F-Type engine. I had worked on engine design before coming to Honda, but not internal combustion engines. I worked on external combustion engines, designing steam locomotives. Then I got started on tiny little 50 cc machines," he said, laughing. "I didn't have any experience with them, but those 2-stroke engines didn't present any great engineering difficulties, so I managed somehow."
This time, however, the engine development would have many difficulties.
Hoshino recalls: "The Super Cub engine came after the Benly J-Type, and it was the second 4-stroke engine I had designed. Nobody in the world was mass-producing anything like a 50 cc 4-stroke engine. It was just accepted that if an engine was a 50 cc, it had to be 2-stroke. When Mr. Honda went to Europe with Mr. Fujisawa, they saw newspapers being delivered to the hotel in the morning, and the vehicles used were all 2-strokes. Apparently the Old Man said, 'That high-pitched exhaust sound is really annoying. They shouldn't be selling machines like that. Bikes like that have really got to be 4-stroke.' The orders I received were, of course, for a 4-stroke engine. After that, he would show up in the Engineering Design Room every single day. I would be absorbed in working out some basic calculations, when all of a sudden I'd glance up and Mr. Honda would be standing there behind me. Often he would be watching over my shoulder without my even realizing it. This happened many times. Talk about turning up the heat, this was much more intense than usual. When we started drawing the engineering plans, it got even worse. For one thing, he could read blueprint drawings very quickly. He would take one glance and say, 'This is no good,' and put a rough pencil stroke right over a part I'd taken great pains to draw cleanly. He had very sharp intuition, so he could perceive problems instantly. There's no doubt about it, his brain wasn't like other people's."
However, Honda was not someone to force his own views on people. He was not a one-sided autocrat, as Hoshino explained:
"For instance, when he said, 'Make this plate here thinner,' if I explained logically that it was that thickness because of our strength calculations, he wouldn't argue. He'd just say, 'Oh, really?' and that was the end of it. It would be a win for me. When the president's idea clashed with ours, we would test it out. 'I guess mine wasn't any good,' he'd say, and lightly let it drop. However, if anyone ever went off-track with their fundamental engineering, then he would be very severe. One time I received a particularly harsh scolding from him. That was when I was testing the supply of lubricating oil to the Benly camshaft, and I got the basic test parameters wrong."
Despite all this, however, the development proceeded as though everyone were under the gun.
"One of our greatest problems was that the engine was to be mounted tilted forward almost to the horizontal," said Hoshino. "No matter what we tried, though, the surface area exposed to moving air was too small, so cooling was problematic. The engine would overheat. Then we thought of opening ventilating holes in the top of the cylinder head cover. That made cooling possible. Mr. Honda would say, 'Creative ingenuity is a wisdom born of suffering,' and he was right.
"I have another, similar story. It happened when we were worried about not getting sufficient power output. The only thing was to enlarge the intake and exhaust valves. But this was a 50 cc engine, so the surface area available in the cylinder head was too small. If we used standard 12 mm-diameter spark plugs, we couldn't increase the diameter of the valves. We decided to take a bold step and use 10 mm plugs. To put it in Mr. Honda's language, 'Common sense is there in order for us to break through it.' NGK, the plug manufacturer, was very positive about developing 10 mm plugs. We got an output of 4.3 PS, so we ended up with about twice as much power as anybody else."
The engine was made a 4-stroke. This was the crucial choice that determined the future of the Super Cub, a future which is still unfolding today.
With an OHV mechanism, the engine had high power and, at 9500 rpm, even higher revolutions than an OHC engine. At the same time, it had the ease of use necessary for a practical bike. The fuel economy also was far superior to 2-stroke engines.