Motorcycles - Motorcycles are produced with both two-stroke- and four-stroke-cycle engines and have up to four cylinders. Most of them are air-cooled, though a few are water-cooled. Their engines are generally limited to 1,200-cubic-centimetre (73-cubic-inch) displacements.

Mopeds - The smallest designs are termed mopeds (from motor pedal), and have very small (50 cubic centimeters) engines offering 100-miles-per-gallon fuel economy. Such units are not permitted on limited-access public roads because of their low speed capability.

Types of motorcycles - Motorcycles are classified into four types in order of increasing power capacity and engine displacements. They are - trail bikes, road bikes, touring bikes, and racing bikes. The highest performance levels in racing are attained by "superbikes" with up to 160 horsepower produced for vehicles weighing approximately 500 pounds.

Frame - The motorcycle frame is often of steel, which is usually a combination of tubes and sheets. The wheels are generally aluminum or steel rims with spokes, although some cast wheels are used. Graphite and magnesium parts are increasingly in use because of high strength-to-weight characteristics.

Tyres - The tyres that are used are similar to those used on automobiles but are smaller and rounded to permit leaning to lower the center of gravity in a turn without losing traction. 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 - 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.