Engine developed with LAF sensors to realize
with 4-stroke engine superior performance and
fuel economy with 4-stroke engine with superior power performance and fuel economy over 2-strokes.

“The main issue was to improve usability, but one direction was to almost double the displacement to 195 cc and cut the peak rpm in half. We thought that if the same maximum output as a two-stroke engine could be achieved at half the rpm, fuel economy would improve even if the displacement was doubled. The goal was to therefore halve fuel consumption,” said Toru Hayashi, a senior researcher at the time.
In addition to the LAF sensor, attempts were made to improve combustion efficiency by reducing heat loss through the use of swirl ports to promote combustion, dual plugs to accelerate flame propagation, and mirror finish of the combustion chamber surface to reduce absorption of radiant heat.
”We also tried direct cylinder fuel injection. In this case, very fine fuel particles must be injected in a short time, so high-pressure injection is necessary. However, if we just injected at high pressure, the fuel would accumulate on the cylinder wall and form lumps. It was very difficult to adjust that part of the injection, but we managed to make it work. But, there were no manufacturers willing to make the small fuel pumps to be installed in the Super Cub. They must have been overwhelmed as at that time, direct fuel injection was gaining attention in the field of F1 racing engines,” said Hayashi.
Many new mechanisms were developed to reduce friction to improve fuel economy, including roller rocker arms, offset cylinders, and offset port technology. Hydroforming (hydraulic molding) was also developed for the body to reduce weight. In addition, the tire pressure, pattern, and compound were reviewed to reduce rolling resistance, the screen and front cover were slanted to reduce aerodynamic drag, and the seat height was lowered by 45 mm. The result was a 52% reduction in fuel consumption compared to existing models.
“We achieved our goal, but the 200 cc Cub was amazing in a sense. For example, a 100 cc engine runs at 6,000 rpm, but a 200 cc engine would rev at 3,000 rpm, so it had a very strong torque (combustion) feeling. When Kawamoto, president at the time, test rode it, he came back after one lap and said, ‘Is this a Cub?’” recalled Hayashi.
In the end, this research was ended with the confirmation of its effectiveness in field tests in Asia, the largest market for the Super Cub series, at a motorcycle R&D center in Bangkok, Thailand.
“Hydroformed frames increased design freedom in terms of strength and rigidity balance, while at the same time simplifying the frame structure, and the total body weight could be reduced by approximately 20%. We could introduce this method in Indonesia, Vietnam and Thailand, which are large markets, with a little investment. However, since the Super Cub series is also produced in Cambodia, Malaysia, and the Philippines, it was difficult (in terms of cost-effectiveness) to introduce the technology there, and in the end, it had to be a partial frame modification evolution. This is the difficulty of having 16 production sites around the world,” said Hayashi.
These technologies and findings from R&D efforts were later adopted in many models. In 2000, Honda declared its intention to go four-stroke, and the new Super Cub series reflected the research conducted at that time. Around the same time, research was also conducted on the cone CVT, which had no gearshift shock due to the infinitely variable drive train gear ratio, and the world’s smallest torque converter designed for the Wave 125.