Honda Super Cub - Design

Design

The Super Cub has been compared to the Ford Model T, Volkswagen Beetle and the Jeep as an icon of 20th century industry and transport. The C100 used a pressed steel monocoque chassis, with the horizontal engine placed below the central spine, a configuration now called the 'step through' or 'underbone' motorcycle. By some criteria, the type of motorcycle the Super Cub falls into is difficult to classify, landing somewhere between a scooter and a motorcycle, and sometimes it was called a moped, "step-thru", or scooterette.

The instruments of a 1966 CA100 and 2009 Super Cub 110

A plastic fairing ran from below the handlebars and under the footpegs, protecting the rider's legs from wind and road debris, as well as hiding the engine from view. This design was like the full enclosure of a scooter, but unlike a scooter the engine and gearbox unit was not fixed to the rear axle. This had several benefits. It moved the engine down and away from the seat, detaching the rear swingarm motion from the drivetrain for lower unsprung weight, and also made engine cooling air flow more direct, and it made possible larger wheels. Placing the engine in the center of the frame, rather than close to the rear wheel, gave it proper front-rear balance. The fuel tank was located under the hinged seat, which opened to reveal the fuel filler inlet. The 17 inch wheels, in comparison to the typical 10 inch wheels of a scooter, were more stable, particularly on rough roads, and psychologically made the motorcycle more familiar, having an appearance closer to a bicycle than a small-wheel scooter.

The pushrod overhead valve (OHV) air-cooled four stroke single cylinder engine had a 40-by-39-millimetre (1.6 in × 1.5 in) bore × stroke, displacing 49 cubic centimetres (3.0 cu in), and could produce 3.4 kilowatts (4.5 hp) @ 9,500 rpm, for maximum speed of 69 km/h (43 mph), under favorable conditions. The low compression ratio meant the engine could consume inexpensive and commonly available low octane fuel, as well as minimizing the effort to kick start the engine, making the extra weight and expense of an electric starter an unnecessary creature comfort. Though some of the many Super Cub variations came with both kick and electric start, the majority sold well without it, and even the latest 2011 model year Japanese domestic market (JDM) Super Cub 50 and Super Cub 110 versions, using up to date technology like Honda's Programmed fuel injection (PGM-FI) and convenience features like a fuel gauge, were not offered with an electric start option.

The sequential shifting three speed gearbox was manually shifted, but clutchless, without the need for a clutch lever control, using instead a centrifugal clutch along with a plate clutch slaved to the footchange lever to engage and disengage the gearbox from the engine. While not intuitive to learn, once the rider got used to it, the semi-automatic transmission, "took the terror out of motorcycling" for novice riders. Unlike many scooter CVTs, the centrifugal clutch made it possible to push start the Super Cub, a useful advantage if the need arose.

The early Super Cubs used a 6 volt ignition magneto mounted on the flywheel, with a battery to help maintain power to the lights, while later ones were upgraded to capacitor discharge ignition (CDI) systems. The lubrication system did not use an oil pump or oil filter, but was a primitive splash-fed system for both the crankcase and gearbox, with a non-consumable screen strainer to collected debris in the engine oil. Both the front and rear brakes were drums. On both the front and rear wheels were 2.25" × 17" wire spoke wheels, with full-width hubs.

Honda recommended daily checks of the lights, horn, tire pressure, brakes, fuel and oil level, and a weekly check of the battery electrolyte level. The new engine break in maintenance was done at 320 kilometres (200 mi), requiring adjustment of the valve tappets and contact breaker points, and an oil change, and the rider was advised to stay under 48 kilometres per hour (30 mph) for the first 800 kilometres (500 mi). Every 1,600 kilometres (1,000 mi) the spark plug needed cleaning, and the chain adjustment checked, and every 3,200 kilometres (2,000 mi) an oil change, breaker point check, and valve adjustment was due. At 8,000 kilometres (5,000 mi), major maintenance was due, requiring the removal and cleaning of the carburetor, drive chain, exhaust silencer, and wheel bearings. The rider closed a manual choke to aid in starting at cold temperatures. By the standards of the day, this was an extremely simple motorcycle, with minimal maintenance demands, and it earned a reputation for high reliability.