Scooters are two-wheeled motor vehicles that have evolved from their classic roots combing a step-through frame, small wheels (10" to 16" in diameter), and rear swingarm-mounted engine suitable for light duty — to a broad range of modern designs that include step-through as well as step-over frames, small or large wheels, front fairings or floor boards, and manual or automatic transmissions — suitable for a range of duty from urban to highway.
Scooters such as the Vespa LX series reflects the scooters' historical antecedents: small wheels, floor boards, front fairing, inner fairing storage. By contrast, the Honda Big Ruckus features no bodywork, floorboards or step-through frame, but remains classified as a scooter due to its smaller wheels and engine placement. The Piaggio MP3, with two front wheels (three wheels total) reflects the fluid nature of the scooter classification. Scooter engine displacements range from under 50 cc to over 799 cc, and some have engine locations in stark contrast to classic scooter design (e.g. Yamaha T-Max 500, Suzuki Burgman 650, Gilera GP800).
Regulatory classification
Scooters world-wide meet highly varied regulatory climates. In Europe, special classifications allow riders of scooters under 250cc to use automobile drivers licensing, and allow special insurance rates.
In the United States the term "scooter" is rarely stipulated as a motor vehicle classification — which usually are based on characteristics instead such as engine size, power, and maximum speed. In the U.S. and Europe, scooters fall into either "motorcycles" or "moped" category depending on their engine characteristics, and each subject to laws for their respective category.
The United States Department of Transportation defines a scooter as having a platform for the operator's feet or has integrated footrests, and has a step-through architecture.
Description
The classic scooter design features a step-through frame and a flat floorboard for the rider's feet. This design is possible because the scooter engine and the drive system transferring power to the rear wheel is attached to the rear axle or under the seat. Unlike a motorcycle, in which the engine is mounted on the frame, this front-hinged arrangement allows the engine to swing vertically together with the rear wheel. Most vintage scooters and some newer retro models have axle-mounted engines with a manual transmission and the gear shift and clutch controls built into the left handlebar. Most newer scooters use a Continuously Variable Transmission (CVT).
Unlike most motorcycles, scooters usually feature bodywork, including a front leg shield and body that conceals all or most of the mechanicals. There is often some integral storage space, either under the seat, built into the front leg shield, or both. Most modern motor scooters have smaller wheels than motorcycles, 12 to 15 inches (30 to 37.5 cm) in diameter, although maxi- and big-wheel scooters may have larger wheels. Most scooters have smaller engines than motorcycles, 50 cc to 400 cc with a single cylinder, although larger models have twin cylinder 400 to 800 cc. motors.
Most jurisdictions have no legal definition for scooters, and instead classify scooters with engines smaller than 50 cc as mopeds, and subject them to lower safety restrictions and licensing fees. Scooters above 50 cc are usually legally considered motorcycles, although some jurisdictions have an in-between definition for motorized bike for scooters and motorcycles between 50 and 150 cc.
Until recently, most modern motor scooters came with air-cooled two-stroke cycle engines with automatic two-stroke oil injection although some of the higher spec small ones and large ones are water cooled, such as the Honda FC50, the 2002 Yamaha YQ50. Scooters increasingly have four-stroke engines, such as Honda GY6, to meet stricter emissions controls. Trends around the world have seen new variations on the classic scooter, some with larger engines and tires. High-end scooter models now include comprehensive technological features, including cast aluminum frames, engines with integral counter-balancing, and cross-linked brake systems. Some of these scooters have comfort features such as an alarm, start button, radio, windshield, heated hand grips and full instrumentation (including clock or outside temperature gauge).
In an effort to reduce emissions, there are now LPG powered scooters that run on liquefied petroleum gas (LPG) instead of gasoline or diesel. High-powered electric road scooters are on the horizon since small electric motorcycles like the Vectrix, e-max, and the eGO have been released