An underbone motorcycle uses structural tube framing with an overlay of plastic or non-structural body panels in contrast with monocoque or unibody designs where pressed steel or tubular steel serves both as the vehicle's structure and bodywork.
Underbone may also refer to a class of small light motorcycles that use the construction type, known variously as step-throughs or scooters.
An underbone cycle may share its fuel tank position and tube framing, along with fitted bodywork and splash guards with a scooter while the wheel size, engine position, and power transmission are like those of larger motorcycles. Underbones are popular worldwide, especially in the developing world.
Although the Super Cub was a step-through design with a small engine, I wouldn’t call it a “scooter” since the rider put his or her feet on pegs rather than a floorboard and the tires were much larger than most scooters. I always called them “motorbikes” to differentiate the Cub from a larger motorcycle.
The Super Cub has been in continuous manufacture since 1958, with production surpassing 60 million in 2008. That makes the Super Cub the most produced motor vehicle in history.
The Super Cub's US advertising campaign, "You meet the nicest people on a Honda," had a lasting impact on Honda's image and on American attitudes about motorcycling, and is considered a classic case study in marketing.
The idea for a new 50 cc (3.1 cu in) motorcycle was conceived in 1956, when Honda Motor's Soichiro Honda and Takeo Fujisawa toured Germany and witnessed the popularity of mopeds and lightweight motorcycles. Soichiro Honda was primarily the engineering and production leader of the company, always with an eye towards winning on the racetrack, while his close partner Fujisawa was the man of finance and business, heading up sales and formulating strategies intended to dominate markets and utterly destroy Honda Motor's competitors.
Fujisawa had been thinking about a long term expansion strategy, and, unlike other Japanese companies, did not want to simply boost production to cash in on the recent economic boom in Japan. A small, high performance motorcycle was central to his plans. Upwardly mobile consumers in postwar Europe typically went from a bicycle to a clip on engine, then bought a scooter, then a bubble car, and then a small car and onwards. Fujisawa saw that a motorcycle did not fit in this pattern for the average person, and he saw an opportunity to change that. Soichiro Honda was at the time tired of listening to Fujisawa talk about his new motorcycle idea; Honda came to Europe to win the Isle of Man TT race and wanted to think about little else.
Fujisawa and Honda visited Kreidler and Lambretta showrooms, as well as others, researching the kind of motorcycle Fujisawa had in mind. Fujisawa said the designs had "no future" and would not sell well. His concept was a two wheeler for everyman, one that would appeal to both developed and developing countries, urban and rural. The new motorcycle needed to be technologically simple to survive in places without up-to-date know-how and access to advanced tools or reliable spare parts supplies. The common consumer complaints of noise, poor reliability, especially in the electrics, and general difficulty of use would have to be addressed.
Because Honda was a large company growing larger, it need a mass appeal product that could be produced on an enormous scale. The design had to be sorted out before production began, because it would be too costly to fix problems in the vast numbers that were to be manufactured. This philosophy was quite the opposite from motorcycle companies in the US and Great Britain where incremental improvement on basic designs several decades old were the norm. Many of these companies operated with a process not much beyond hand-built and mass production was often not at the front of their thinking.
My personal experience with Japanese engineering in the 70’s and 80’s emphasized this fact. While IBM was big on small improvements and engineering changes, the Japanese tended to create a product from a carefully implemented process, and then not change it. Often these little changes would have unintended consequences, and I think the Japanese often had the right idea … do it right the first time and then don't "fiddle" with it.
The scooter type nearly fitted the bill for the Honda corporation, but was too complex for developing countries to maintain, and the small wheels did poorly on badly maintained or nonexistent roads. Another of Fujusawa's requirements was that it could be ridden with one hand while carrying a tray of soba noodles, saying to Honda, "If you can design a small motorcycle, say 50 cc with a cover to hide the engine and hoses and wires inside, I can sell it. I don't know how many soba noodle shops there are in Japan, but I bet you that every shop will want one for deliveries." That may have been a key motivation for the Super Cub's centrifugal clutch and foot shift which freed the left hand.
Once interested, Soichiro Honda began developing the Super Cub on his return to Japan.The following year Honda displayed a mockup to Fujisawa that finally matched what he had in mind, Fujisawa declaring the annual sales would be 30,000 per month, half again as many as the entire monthly two-wheeler market in Japan. His goal was export on a scale yet unseen in the economic disorder of postwar Japan, when most companies' halting trade efforts were handled through foreign trading companies. Honda would have to establish its own overseas subsidiary to provide the necessary service and spare parts distribution in a large country like the United States. To this end American Honda Motor Company was founded in 1959. In 1961 a sales network was established in Germany, then in Belgium and the UK in 1962, and then France in 1964.
The Honda Juno had been the first scooter to use polyester resin, or fiberglass reinforced plastic (FRP), bodywork, and even though production of the Juno had stopped in 1954 as a result of Honda Motor's financial and labor problems at the time, Fujisawa continued to encourage research in polyester resin casting techniques, and these efforts bore fruit for the Super Cub.
The new motorcycle's fairing would be polyethylene, the most widely used plastic, which reduced weight over FRP, but Honda's supplier had never made such a large die cast before, so the die had to be provided by Honda. The Super Cub was the first motorcycle ever to use a plastic fairing. Motorcycling historian Clement Salvadori wrote that the plastic front fender and leg shields were, "perhaps the Cub's greatest contribution; plastic did the job just as well as metal at considerably lower cost."
The technology developed in the Isle of Man TT racing program was equally vital to the new lightweight motorcycle, making possible 4.5 hp from a 50 cc four-stroke Honda engine, where the first engine the company built a decade earlier, a "fairly exact copy" of the 50 cc two stroke war-surplus Tohatsu engine Honda had been selling as motorized bicycle auxiliary engine, had only a 0.5–1 hp output. Certainly my first 50 cc bike, a Puch MoPed sold by Sears, got a fraction of the power that Honda could wring from the same displacement. Honda’s first four stroke, the 1951 E-type, had just a little more power than the Super Cub, 5 bhp, with nearly triple the displacement, 146 cc (8.9 cu in). So the Super Cub engine was a marvel of power for such a small size and a leap forward foretelling things to come.
To make the new motorcycle, Honda built a new ¥10 billion factory in Suzuka, Mie to manufacture 30,000, and with two shifts, 50,000, Super Cubs per month. The factory was modeled on the Volkswagen Beetle production line in Wolfsburg, Germany.
Until then, Honda's top models had sold only 2,000 to 3,000 per month, and observers thought the cost of the new plant too risky an expenditure. Edward Turner of BSA went to Japan to see the motorcycle industry in September 1960, and said that investments the size of the Suzuka plant were "extremely dangerous" because he considered the US motorcycle market already saturated.
When completed in 1960, the Suzuka Factory was the largest motorcycle factory in the world, and was a model for Honda's mass production facilities of the future. The economies of scale achieved at Suzuka cut 18% from the cost of producing each Super Cub when Suzuka could be run at full capacity, but in the short term Honda faced excess inventory problems when the new factory went into operation before the full sales and distribution network was in place.
The pushrod overhead valve (OHV) air-cooled four stroke single cylinder, 49 cc engine could produce 4.5 hp @ 9,500 rpm, for maximum speed of 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 2011 model year Japanese domestic market 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 foot-change 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 transmissions, the centrifugal clutch made it possible to push start the Super Cub, a useful advantage if the need arose. Owners quickly learned you could hold down the foot shifter and rev the engine before releasing the shifter to get a fast start equal to a hand clutch. My MoPed was shifted by pulling in the left-hand clutch lever and then rotating the grip from first to second. The Honda design was obviously superior, especially for a small bike.
The early Super Cubs used a simple 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, and the front and rear wheels were 17" wire spoke with full-width hubs just like a "real" motorcycle.
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 200 miles, requiring adjustment of the valve tappets and contact breaker points, and an oil change. Every 1,000 miles the spark plug needed cleaning, and the chain adjustment checked, and every 2,000 miles an oil change, breaker point check, and valve adjustment was due. At 5,000 miles major maintenance was performed, 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.
The C110 Sports Cub debuted in October 1960. The C110 was more like a traditional motorcycle that the rider had to straddle, not a step-through. It had a different frame, with the fuel tank in the on top of the frame and in front of the seat, and the frame's steel tube spine ran horizontally from the head tube to the seat. It had a hand clutch and a foot shifter more like larger bikes, but shared the same basic engine with the C100. It had a bit more power, increased from 4.5 to 5 bhp @ 9,500 rpm. An on- and off-road version of the step-through Super Cub came out in 1961. It would be classed as a dual-sport motorcycle today, but Honda called it a trail bike, the CA100T Trail 50.
Such was the success of the Super Cub motorbike in the US and all over the world that many riders today will tell fondly of their first bike, a Honda Super Cub. These bikes hit my hometown in the early ‘60s and seemed like everyone had one. I was envious of the 110 which looked more like a classic motorcycle and it wasn’t long before I owned a 150 cc Honda “Benly Super Sport” twin (CB92). Sharing much of the frame and front shock design with its little brother Sports Cub, this was my first taste of a “real” motorcycle. I actually raced that bike and won a trophy for first place at the Lewistown (King Kam Dragway) Quarter Mile Races. Don’t let the fact that I was the only entry in the 150 cc class tarnish this accomplishment. Now where did I put that trophy?
My brother, Dale, had the 305 cc "Dream." A white one and definitely a respectable ride upon which you would meet the nicest people.
In the end both Soichiro Honda and Takeo Fujisawa were satisfied. Honda got the racing platform and success he yearned and Fujisawa saw the motorcycle trade grow his company into the world leading transportation empire it is today.
I’ll bet they were singing along with the Beach Boys:
It's not a big motorcycle
Just a groovy little motorbike
It's more fun that a barrel of monkeys
That two wheel bike
We'll ride on out of the town
To any place I know you like
It climbs the hills like a Matchless
Cause my Honda's built really light
When I go into the turns
Lean with me and hang on tight
I better turn on the lights
So we can ride my Honda tonight
First gear (Honda Honda) it's alright (faster faster)
Second gear (little Honda Honda) I lean right (faster faster)
Third gear (Honda Honda) hang on tight (faster faster)
Faster it's alright