- A motorcycle is powered by its drivetrain. This includes the engine, which is almost always an internal combustion engine that uses conventional gasoline as fuel. Motorcycle engines are usually centrally mounted below the driver's seat. A carburetor blends fuel with air before it is drawn into the ending for combustion, though some high end models now use fuel injectors in place of carburetors.
A motorcycle's engine conveys power to the rear drive wheel through its transmission. The transmission itself is attached to the engine, and operated by a shift lever (usually a lever attached to one of the handlebars) and a clutch (usually a pedal operated by the left foot). The system connecting the transmission to the rear wheel (the final drive) varies on different types of motorcycles, and may be a chain or belt, or a solid shaft. - Traditionally, motorcycle wheels featured steel spokes, but, today, cast aluminum wheels are common. Other alloys are also found on some models. Because of the rear wheel drive configuration, rear wheels may be larger, or at least wider, than front wheels, which are narrower for improved steering. Tires are pneumatic, and often use an inflatable rubber tube inside of the thicker rubber tread. Tread patterns vary widely, and are designed for driving on different surfaces, or under different conditions.
Motorcycles may feature either drum or disc brakes. Typically, disc brakes are offered on high end models or heavier motorcycles that require more powerful brakes. Brakes are controlled by a hydraulic system that is activated by handlebar or foot levers. Some motorcycles also feature an anti-lock brake system like those used in cars and trucks. - Motorcycle manufacturers use several configurations for the chassis that serves as the basis for a motorcycle. Steel and aluminum are used in the construction of most motorcycle frames. Near the front of the frame, the head tube contains the vertical structure of the front fork, which attaches the handlebars above to the front wheel below. Oftentimes, the engine itself is an integrated part of the frame, helping to connect components in front of it to those behind it.
Some motorcycles, such as the "chopper" style, employ a rigid frame without any rear suspension. Most other styles feature both front and rear suspension in the form of shock absorbers located inside the forks or just above the wheels. Motorcycles designed for off-road use may include more robust suspension systems featuring high performance shock absorbers or supplemental coil springs. - Modern motorcycles can have extremely complex electrical systems. Motorcycle batteries are positioned in any number of places, wherever the bike's design allows space for them to be mounted. Some of the most basic electrical components are the lights, which include the headlight(s), tail lights, directional signals and brake lights. Beyond lighting, instrumentation is an important part of the electrical system. This includes the speedometer, tachometer and odometer. A fuel gauge is less common, but included on some models. Oil pressure gauges, engine temperature gauges and full computerized trip data centers are also available on certain motorcycles. Finally, radios or GPS navigation systems may be part of a motorcycle's instrumentation.
Some modern engines also feature electrical systems beyond simply the spark plugs. Fuel injectors, temperature sensors and variable valve timing are all optional engine systems that may make use of an electrical system. - Additionally, motorcycles feature relatively simple exhaust systems, gas tanks and seating surfaces. Other components may be added to distinguish one model from another, or to prepare a motorcycle for a certain type of driving. Plastic or fiberglass bodywork often gives motorcycles a streamlined appearance and aerodynamic profile, while performing little practical purpose. Fairings, which may include a windshield, serve a similar purpose, while giving the driver a degree of protection from the elements.
For long range driving, storage solutions like hard-sided saddlebags, top cases and tow-behind trailers are offered as aftermarket accessories for many motorcycles.
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