Types of motorcycles
There are many systems for classifying types of motorcycles, describing how the motorcycles are put to use, or the designer's intent, or some combination of the two. Six main categories are widely recognized: cruiser, sport, touring, standard, dual-purpose, and dirt bike. Sometimes sport touring motorcycles are recognized as a seventh category. Strong lines are sometimes drawn between motorcycles and their smaller cousins, mopeds, scooters, and underbones, but other classification schemes include these as types of motorcycles.
There is no universal system for classifying all types of motorcycles. There are strict classification systems enforced by competitive motorcycle sport sanctioning bodies, or legal definitions of a motorcycle established by certain legal jurisdictions for motorcycle registration, emissions, road traffic safety rules or motorcyclist licensing. There are also informal classifications or nicknames used by manufacturers, riders, and the motorcycling media. Some experts do not recognize sub-types, like naked bike, that "purport to be classified" outside the six usual classes, because they fit within one of the main types and are recognizable only by cosmetic changes.
Street motorcycles are motorcycles designed for being ridden on paved roads. They have smooth tires with a light tread pattern and engines generally in the 125 cc (7.6 cu in) and over range. Most are capable of speeds up to 100 mph (160 km/h), and many of speeds in excess of 125 mph (201 km/h).
Standards, also called naked bikes or roadsters, are versatile, general purpose street motorcycles. They are recognized primarily by their upright riding position, partway between the reclining rider posture of the cruisers and the forward leaning sport bikes. Footpegs are below the rider and handlebars are high enough to not force the rider to reach far forward, placing the shoulders above the hips in a natural position. Because of their flexibility, lower costs and their engines of moderate output, standards are particularly suited to motorcycle beginners 
Standards usually do not come with fairings or windscreens, or if they have them, they are relatively small. Standard is often a synonym for naked bike, a term that became popular in the 1990s in response to the proliferation of fully faired sport bikes. The standard seemed to have disappeared, fueling nostalgia for the return of the Universal Japanese motorcycle (UJM), which were admired for their simplicity, quality, and versatility.
Muscle bike is a nickname for a motorcycle type, derived from either a standard or sport bike design, that puts a disproportionately high priority on engine power. Roadster is an older term, equivalent to standard or naked.
Cruisers are styled after American machines from the 1930s to the early 1960s, such as those made by Harley-Davidson, Indian, and Excelsior-Henderson. Harley-Davidsons largely define the cruiser category, and large-displacement V-twin engines are the norm, although other engine configurations and small to medium displacements also exist. Their engines are tuned for low-end torque, making them less demanding to ride because it is not necessary to shift as frequently to accelerate or maintain control. Cruisers are sometimes called "custom" even in the absence of aftermarket modifications.
The riding position places the feet forward and the hands are up relatively high, so that the spine is erect or leaning back slightly. At low to moderate speeds, cruisers are more comfortable than other styles, but riding for long periods at freeway speeds can lead to fatigue from pulling back on the handlebars to resist the force of the wind against the rider's chest. Cruisers have limited cornering ability due to a lack of ground clearance.
Choppers are a type of cruiser, so called because they are a "chopped", or cut-down, version of a production cruiser. Choppers are usually custom projects that result in a bike modified to suit the owner's ideals, and, as such, are a source of pride and accomplishment. Stereotypically, a chopper may have raked-out forks, small fuel tanks and high handlebars. Choppers were popularised in the Peter Fonda film Easy Rider. Being designed primarily for visual effect, choppers will not usually be the most efficient riding machines.
Power cruiser is a name used to distinguish bikes in the cruiser class that have significantly more engine output, around 80–100 hp (60–75 kW) as opposed to about 50–70 hp (37–52 kW). They often come with upgraded brakes and suspensions, better ground clearance, and premium surface finishes, as well as more exotic or non-traditional styling.
Sport bikes emphasize speed, acceleration, braking, and cornering on paved roads, typically at the expense of comfort and fuel economy in comparison to less specialized motorcycles. Because of this, there are certain design elements that most motorcycles of this type will share. Sport bikes have comparatively high performance engines resting inside a lightweight frame. Inline-four engines dominate the sport bike category, with V-twins having a significant presence, and nearly every other engine configuration appearing in small numbers at one time or another. The combination of these elements helps maintain structural integrity and chassis rigidity. Braking systems combine higher performance brake pads and multi-piston calipers that clamp onto oversized vented rotors. Suspension systems are advanced in terms of adjustments and materials for increased stability and durability. Most sport bikes have fairings, often completely enclosing the engine, and windscreens that effectively deflect the air at very high speeds, or at least reduce overall drag.
Sport bikes have high footpegs that position the legs closer to the body to improve ground clearance when cornering, and a long reach to the hand controls, which positions the body and center of gravity forward, above the fuel tank. The rider leans forward into the wind, the force of which can comfortably support the rider's weight at speeds near 100 mph (160 km/h), but at lower speeds leaves too much weight on the arms and wrists, causing fatigue.
Streetfighters are derived from sport bikes, originally being customized sport bikes with the fairings removed and higher handlebars replacing the low clip-on handlebars. Since the 1990s, factory streetfighters have been produced. As with naked bike and muscle bike (below), the name streetfighter is used to help clarify the middle ground occupied by designs that blend elements of both sport bikes and standards.
Although any motorcycle can be equipped and used for touring, touring motorcycles are specifically designed to excel at covering long distances. They have large-displacement engines, fairings and screens that offer good weather and wind protection, large-capacity fuel tanks for long ranges between fill-ups, and a relaxed, upright seating position. Passenger accommodation is excellent and expansive luggage space is the norm for this class. Such bikes can have wet weights of 850–900 lb (390–410 kg) and top 1,300–1,400 lb (590–640 kg) fully loaded with a rider, passenger, and gear.
Bagger, full dresser, full dress tourer, or dresser are various names for touring motorcycles, sometimes used disparagingly or jocularly, and originally referring to a Harley-Davidson or other cruisers with full sets of saddlebags. Now refers to any touring motorcycle.
Sport touring motorcycles combine attributes of sport bikes and touring motorcycles. The rider posture is less extreme than a sport bike, giving greater long-distance comfort. Accommodation for a passenger is superior to a sport bike as well, along with luggage capacity. Being lighter, at 550–720 lb (250–330 kg) wet, than a pure touring bike and often having racier engines, suspensions, and brakes, sport tourers corner better and are more at home being aggressively ridden on curvy canyon roads. The distinction between touring and sport touring is not always clear as some manufacturers will list the same bike in either category in different markets. The Honda ST1300 Pan-European, for example, was listed by Honda as a sport touring motorcycle in the United States and Australia, but as a touring motorcycle in Europe.
Dual-sports, sometimes called dual-purpose or on/off-road motorcycles, are street legal machines that are also designed to enter off-road situations. Typically based on a dirt bike chassis, they have added lights, mirrors, signals, and instruments that allow them to be licensed for public roads. They are higher than other street bikes, with a high center of gravity and tall seat height, allowing good suspension travel for rough ground.
Adventure motorcycles are motorcycles with touring capability on paved and unpaved roads. As a dual-sport they have a significant on-pavement bias and perform well on pavement at higher speeds unlike most dual-sports. Their size, weight and sometimes their tires, however, limits their off road capability. Most adventure motorcycles function well on graded dirt and gravel roads but are less than ideal on more difficult off-pavement terrain.
Supermoto motorcycles were designed to compete on a single course that alternated between three genres of motorcycle racing: road racing, track racing, and motocross. This increasingly popular type of motorcycle is often a dual-sport that has been fitted by the manufacturer with smaller rims and road tires. Supermotos are quickly gaining popularity as street bikes due to their combination of light weight, durability, relatively low cost, and sporty handling.
Scooters, underbones and mopeds
Scooter engine sizes range smaller than motorcycles, 50–850 cc (3.1–51.9 cu in), and have all-enclosing bodywork that makes them cleaner and quieter than motorcycles, as well as having more built-in storage space. Automatic clutches and continuously variable transmissions (CVT) make them easier to learn and to ride. Scooters usually have smaller wheels than motorcycles. Scooters usually have the engine as part of the swingarm, so that their engines travel up and down with the suspension.
Underbones are small-displacement motorcycle with a step-through frame, descendants of the original Honda Super Cub. They are differentiated from scooters by their larger wheels and their use of footpegs instead of a floorboard. They often have a gear shifter with an automatic clutch.
The moped used to be a hybrid of the bicycle and the motorcycle, equipped with a small engine (usually a small two-stroke engine up to 50 cc, but occasionally an electric motor) and a bicycle drivetrain, and motive power can be supplied by the engine, the rider, or both. There is also Sport mopeds – a type of moped that resembles a sport bike.
In many places, mopeds are subject to less stringent licensing than bikes with larger engines and are popular as very cheap motorbikes, with the pedals seeing next to no use. Mopeds were very popular in the United States during the fuel-crisis of the late 1970s and early 1980s, but their popularity has fallen off sharply since the mid-1980s. In response to rising fuel prices in the first decade of the 2000s, U.S. scooter and moped ridership saw a resurgence. Sales of motorcycles and scooters declined 43.2% in 2009, and continued to decrease in the first quarter of 2010, with scooter sales doing worst, down 13.3% compared to a 4.6% drop for all two-wheelers.
There are various types of off-road motorcycles, also known as dirt bikes, specially designed for off-road events. Compared to road-going motorcycles, off-road machines are simpler and lighter, having long suspension travel, high ground clearance, and rugged construction with little bodywork and no fairings for less damage in spills. Wheels (usually 21" front, 18" rear) have knobby tires, often clamped to the rim with a rim lock.
There are specialized motorcycles for a variety of off-road motorcycle sports:
- Motocross — Such bikes (once called "scramblers") are raced on short, closed off-road tracks with a variety of obstacles. The motorcycles have a small fuel tank for lightness and compactness. Long-travel suspension allows riders to take jumps at high speed. Motocross engines are usually single-cylinder two-stroke or four-stroke units, which vary in size from 50cc up to about 650cc. Motocross sidecar outfits have bigger engines, usually four-stroke and often twin-cylinder. Motocross bikes are also used in Freestyle Motocross.
- Enduro — A modified and road-legal motocross bike, having the addition of a horn, lights, effective silencing and a number plate. Enduro riders compete over a longer course (which may include roads); and an enduro event may last between one day and six days (such as the ISDE). Some enduro events (known as "multi-lappers") are held on rather shorter circuits, not unlike scramble tracks. "Multilappers" are especially popular with novice riders.
- Rally raid, or "Rallies" — A special type of enduro bike with a significantly larger fuel tank for very long distance racing, typically through deserts (e.g. Paris-Dakar rally). Engine capacities tend to be larger, usually between 450 cc and 750 cc.
- Trail — A trail bike is a dual-purpose bike, made for on-road and recreational off-road riding. A trail bike may resemble an enduro bike, but since a trail bike is not intended to be used for competition, it may be (i) less rugged, and (ii) equipped with dual-purpose tyres and with more road legal equipment, such as indicators, mirrors and extra instruments.
- Trials — Trials riding is a specialized form of off-road competition testing balancing skills and precision rather than speed. For a trials bike, low weight and crisp throttle response power are the priorities, so a trials bike tends to have a small (125 cc to 300 cc) engine, two-strokes being common. During the trial, the rider stands on the footpegs, so a trials bike will have only a vestigial seat, or even no seat at all. Fuel tanks are very small, giving a very limited range.
- Track racing — High-speed oval racing, typically with no brakes, nor rear suspension. The engines, fuelled by methanol, are long-stroke four-stroke singles, such as JAP or Jawa. They have at most two gears. Some types, such as speedway, and grass-track bikes, are designed to take left turns only.
There are speciality motorcycles adapted to job functions, like police motorcycles, motorcycle ambulances, military motorcycles, dernys for use in track cycling events, and motorcycles used for towing cars.
Feet forwards motorcycles are an experimental configuration – an example is the Quasar. While motorcycles typically have two wheels, powered tricycles are three-wheeled motorcycles. Some brands have made various types of three-wheelers direct from the factory. Most of these vehicles are treated as motorcycles for purposes of registration or licensing. Early cyclecars, with four wheels, were constructed more like motorcycles than cars, and were sometimes treated as a kind of motorcycle.
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Streetfighter -- Also known as a 'hooligan' cycle, this is a sports-bike stripped of all superfluous bodywork.
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streetfighter: a type of superbike customized for maximum speed and performance.
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