Motorcycle

A

Street Motorcycles

Street motorcycles are intended primarily for everyday riding. They have all the required safety equipment for use on public highways, such as lights, mirrors, a horn, and a muffler. Their tires have a tread pattern that provides good traction on both dry and wet surfaces.

There are two chief kinds of street motorcycles: sport touring motorcycles and cruising motorcycles. Sport touring motorcycles typically have wind guards, or fairings, around the headlight and engine to enhance styling and reduce drag; short, straight handlebars; and a seat shape and position that causes the rider to lean forward over the gas tank. In contrast, cruisers have no fairings around the headlights or engine and have deep handlebars and a seating position that allows the rider to sit upright. Most cruisers also have a V-configuration engine. During the 1950s, 1960s, and 1970s, customized cruisers called choppers were popular. Choppers have lengthened front forks and high handlebars.

Police officers typically ride custom-built cruisers with large 1200 cc engines. Police motorcycles are usually equipped with two-way radios, flashing lights, and police emblems so that motorists can easily identify them as official police vehicles. Many also have a windscreen or front fairing and extra cargo compartments for carrying emergency gear.

B

Off-Road Motorcycles

In comparison to street motorcycles, off-road motorcycles have narrower, lighter frames, increased ground clearance, and sophisticated suspension systems. Most are powered by single cylinder, two-stroke or four-stroke engines with displacements ranging from 250 to 500 cc. They often have a kick-starter rather than an electric starter to reduce weight. Large diameter tires with a knobby tread pattern provide increased traction, and a large gear on the rear wheel multiplies engine torque for climbing hills. Straight, wide handlebars provide extra leverage. If used strictly for off-road riding, the cycle may not have lights, mirrors, a horn, or a muffler. Most off-road motorcycles have flexible plastic fenders and fuel tanks to minimize damage in the event of a fall. Riders typically wear extra protective gear, including chest, knee, elbow, and shin protectors.

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C

Racing Motorcycles

Racing motorcycles are specially designed for closed circuit tracks or road racing. Most motorcycles designed for road courses have fiberglass or carbon fiber fairings around the front and engine to improve aerodynamics. They have stiff suspension systems to improve handling agility on curves, and their engines are modified to produce more power. In Europe, two-person racing cycles with sidecars are popular.

Motorcycles used for drag racing are often lengthened to improve high-speed handling stability. Bars extend behind the rear wheel to prevent the front wheel from lifting off the ground during acceleration, which would cause the cycle to flip over. A wide rear tire with no tread maximizes tire contact with the track surface. In some types of motorcycle racing, alcohol or nitromethane fuel may be used instead of gasoline to boost power. Many racing motorcycles can reach speeds as high as 390 km/h (242 mph) from a standing start in a quarter mile.

IV

History

The invention of the motorcycle closely followed the development of the bicycle and the four-stroke gasoline engine. German inventor Gottlieb Daimler created the first motorcycle in 1885. He attached a four-stroke gasoline engine to a wooden bicycle frame and added two extra side wheels for stability, similar to training wheels on a bicycle. Daimler’s engine turned the rear wheel with a pulley.

Various models were introduced in Germany, France, and Britain in subsequent years, each attempting to turn the motorcycle into a practical means of transportation. In 1903 American inventor William Harley, his neighbor Arthur Davidson, and Davidson’s brothers Walter and William built the first Harley-Davidson motorcycle. A year later Harley-Davidson began manufacturing motorcycles for sale. In 1909 Harley-Davidson introduced the first V-Twin engine, which had two cylinders arranged in a distinctive “V” angle. The engine, which produced a deep, rumbling sound, soon became the classic American motorcycle engine.

By 1914 the basic layout of the modern motorcycle was established. This layout featured an engine located between the front and rear wheels and a chain to transfer power from the engine to the rear wheel. During World War I (1914-1918), motorcycles proved a reliable source of transportation for American and European military forces negotiating war-damaged roads and carrying communications to forward positions. Following the war, the use of motorcycles spread rapidly in Europe and the United States.

Through the 1950s most of the motorcycles in North America were manufactured by Harley-Davidson or by British manufacturers, such as the Birmingham Small Arms Company (BSA), Norton, and Triumph. But during the 1960s and 1970s, Japanese manufacturers, including Honda, Kawasaki, Suzuki, and Yamaha, began to introduce motorcycles that had improved engines and suspensions capable of outperforming their American and English counterparts. Powerful inline four-cylinder 750 to 1200 cc engines in Japanese motorcycles soon dominated the street motorcycle market, while their 250 to 500 cc two-stroke engines virtually ruled the market for off-road motorcycles. The highly competitive Japanese manufacturers soon forced most of the English companies out of business. Harley-Davidson almost went out of business as well, but the company was saved from bankruptcy by a special U.S. import tax placed on Japanese motorcycles over 750 cc.

In the 1970s, new pollution emission regulations made many two-stroke engines obsolete. To improve emissions performance, many manufacturers replaced the traditional air-cooled engine with liquid-cooled four-stroke engines. Electronic ignition also replaced contact point ignition systems to improve reliability.

In the 1970s many U.S. states and Canadian provinces adopted helmet laws that required people to wear protective headgear when riding a motorcycle. The helmet laws proved very unpopular with many cyclists and were overturned in some states. The controversy continues today over who should decide whether riders wear helmets. Advocates of helmet laws believe that the government has the right to compel riders on public roads to wear helmets. Opponents argue that this decision should be left entirely to the individual.

In the 1980s some high performance motorcycles with “turbocharged” engines were introduced. A turbocharger uses hot exhaust gases to spin a small turbine blade. The spinning blade pushes more air and fuel into the engine, boosting its power output significantly. In the 1990s fuel injection replaced carburetors on some engines for easier starting, improved fuel economy, and reduced emissions.

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