- Key People:
- Sonny Barger
- Evel Knievel
- Gottlieb Daimler
- Related Topics:
- automotive industry
- CB750
- moped
- Werner
- vehicle
motorcycle
-
What is a motorcycle?
A motorcycle is an automotive vehicle with two in-line wheels. The invention of the motorcycle created the self-propelled bicycle. Motorcycles are produced with both two-stroke- and four-stroke-cycle engines and with up to four cylinders. Most are air-cooled, though a few are water-cooled.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How is a motorcycle different from a car?
While both motorcycles and cars are vehicles, they differ significantly in structure and mechanics. Motorcycles typically have two wheels, though some have three, while cars have four. Motorcycle engines range up to 1,800 cc, using two- or four-stroke cycles, and transmissions have four to six speeds.
Motorcycle frames are often steel, with aluminum or steel rims, and increasingly use graphite and composite parts for strength and weight reduction. Their tires are smaller and rounded to allow leaning during turns. The gyroscopic effect of the wheels enhances stability and cornering.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are the main parts of a motorcycle?
A motorcycle consists of a frame, wheels, engine, and transmission. The frame is often steel, using tubes and sheets. Wheels usually have aluminum or steel rims with spokes, though some use cast wheels. Graphite, composite, and magnesium parts are increasingly common due to their strength-to-weight ratio.
Front-wheel suspension uses coil springs on a telescopic fork. Rear-wheel springs often mount on shock absorbers similar to those in cars. Transmissions typically have four to six speeds, and power is usually sent to the rear-wheel sprockets by a chain, though belts or shafts are sometimes used.
The clutch and throttle, which control engine speed, are operated by twist-type controls on the handgrips. A lever near the handgrip controls the front-wheel brake, while a foot pedal engages the rear-wheel brake. The front brake is usually a hydraulic disc type, and the rear brake may be disc or drum. Electric push-button starters have mostly replaced kick starters.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does a motorcycle engine work?
Most motorcycles have either two-stroke or four-stroke engines, typically air-cooled, with some being water-cooled. The four-stroke cycle, common in modern motorcycle engines, involves four steps:
1. Intake: The piston descends, drawing a fuel-air mixture into the cylinder.
2. Compression: The piston ascends, compressing the mixture with both valves closed.
3. Power: The compressed mixture is ignited by a spark, forcing the piston down and generating power.
4. Exhaust: The piston ascends again, pushing the exhaust gases out through the open exhaust valve.The carburetor supplies the engine with a mixture of fuel and air. The fuel injection system sprays fuel directly into the cylinders, relying on heat from compressed air for ignition (in diesel engines) or using spark plugs (in spark ignition engines).
7 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are some common uses for motorcycles around the world?
Motorcycles serve various purposes worldwide, ranging from basic transportation to competitive racing. Mopeds, with their small engines, offer high fuel efficiency for short commutes. Trail bikes are designed for off-road adventures, while road bikes are built for everyday commuting and touring bikes for long-distance travel. Racing bikes, including superbikes, are optimized for speed and performance on closed circuits. Motorcycle racing includes various forms such as road racing, motocross, speedway, and drag racing.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
motorcycle, any two-wheeled or, less commonly, three-wheeled motor vehicle, usually propelled by an internal-combustion engine.
History
Just as the automobile was the answer to the 19th-century dream of self-propelling the horse-drawn carriage, the invention of the motorcycle created the self-propelled bicycle. The first commercial design was a three-wheeler built by Edward Butler in Great Britain in 1884. It employed a horizontal single-cylinder gasoline engine mounted between two steerable front wheels and connected by a drive chain to the rear wheel.
By 1900 many manufacturers were converting bicycles—or pedal cycles, as they were sometimes called—by adding small, centrally mounted spark ignition engines. The need for reliable constructions led to road motorcycle trial tests and competition between manufacturers. The original Tourist Trophy motorcycle races were held on the Isle of Man in 1907 as reliability or endurance races. Such events have been the proving ground for many new ideas from early two-stroke-cycle designs to supercharged, multivalve engines mounted on aerodynamic, carbon-fibre reinforced bodywork.
" height="20" alt="HEW Logo">
Components
Motorcycles are produced with both two-stroke- and four-stroke-cycle engines and with up to four cylinders. Most are air-cooled, though a few are water-cooled. Engines are generally limited to displacements of about 1,800 cc. The smallest designs, termed mopeds (from “motor pedal”), have very small engines (50 cc) with fuel economies of as much as 2.4 litres per 100 km (100 miles per gallon). Such units are not permitted on limited-access public roads because of their low speed capability. In order of increasing power capacity and engine displacements, the other five classifications are child bikes, trail bikes, road bikes, touring bikes, and racing bikes. A subcategory of racing bikes is known as superbikes. These are motorcycles that displace more than 900 cc and in which the seat is tilted forward so that the rider is hunched over the frame, creating a more aerodynamic profile.
The motorcycle frame is often of steel, usually a combination of tubes and sheets. The wheels are generally aluminum or steel rims with spokes, although some cast wheels are used. Graphite, composite, and magnesium parts are increasingly in use because of their high strength-to-weight characteristics. Tires are similar to those used on automobiles but are smaller and rounded to permit leaning to lower the centre of gravity in a turn without losing traction. The gyroscopic effect of motorcycle wheels rotating at high speed significantly improves stability and cornering ability. Inertia and steering geometry are also significant factors. Front-wheel suspension is provided by coil springs on a telescopic fork; rear-wheel springs are often mounted on shock absorbers similar to those used in automobiles.
Transmissions on motorcycles typically have four to six speeds, although small bikes may have as few as two. Power is normally transmitted to the rear-wheel sprockets by a chain, though occasionally belts or shafts are used.
The clutch and throttle, which control engine speed, are operated by twist-type controls on the handgrips. The front-wheel brake is controlled by a lever near the handgrip; the rear-wheel brake is engaged by a foot pedal. Except on very small machines, the front brake is usually of the hydraulic disc type. The rear brake may be disc or drum. The kick starter has been mostly replaced by an electric push-button starter.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
Emissions standards
Tailpipe emissions standards for motorcycles continue to be strengthened. In 1980 the U.S. Environmental Protection Agency (EPA) first regulated new motorcycle hydrocarbon emissions, requiring motorcycles to emit less than 5.0 grams per km (0.3 ounce per mile) of highway driving. California and the European Union (EU) imposed stricter limits on hydrocarbons and added restrictions on nitric oxides and carbon monoxide. In 2006 emissions from new motorcycles sold in the United States were limited to a combined 1.4 grams of hydrocarbons and nitric oxides and 12.0 grams of carbon monoxide per km. The EPA decreased the limit on combined emissions of hydrocarbons and nitric oxides to 0.8 gram in 2010. The EU reduced emissions from new motorcycles in 2004 to 1.0 gram of hydrocarbons, 0.3 gram of nitric oxides, and 5.5 grams of carbon monoxide per km; in 2007 these levels were further reduced to 0.3 gram of hydrocarbons, 0.15 gram of nitric oxides, and 2.0 grams of carbon monoxide per km. The EU did a further emission reduction in 2016 to 0.17 gram of hydrocarbons, 0.09 gram of nitric oxides, and 1.14 grams of carbon monoxide, with a further reduction to 0.1 gram of hydrocarbons, 0.06 gram of nitric oxides, and 1 gram of carbon monoxide planned for 2020. Although U.S. limits for carbon monoxide were not lowered by law, the required reductions in other pollutants effectively lowered carbon monoxide emissions in fact. In order to meet these “clean-air regulations,” manufacturers installed more sophisticated catalytic converters and fuel-injection systems.