A motorcycle is, at its most basic, a motorised form of personal transport. It consists of an internal-combustion engine, two wheels, steering and somewhere to sit. Its body, called a frame, is usually made from steel. The wheels are smaller than car tires, and they are mounted to the front and rear of the frame. Motorcycles are equipped with a variety of safety features, including headlights, turn signals and horns, as well as brakes.
The engine on a motorcycle is powered by liquid fuel, typically petrol, and generates a maximum of a few hundred horsepower. The engine is housed in a sealed, box-shaped enclosure, and it uses steel or aluminium for its crankcases, cylinders and heads, as well as stainless steel valves and titanium or aluminium camshafts. The power from the engine is transmitted to the rear wheel sprockets through a chain or belt, and is controlled by a throttle, clutch and transmission system, which may have from four to six speeds.
Because they do not have a full enclosure for the rider, motorcycles are not very aerodynamic – their wheels and engine expose them to the wind, and the rider is often exposed as well, which all add up to a lot of drag compared with a smooth, streamlined car. This is not a big issue at low speeds, but it becomes more of a problem as the speed increases.
The best protection that any rider can have is a helmet, and all riders should consider taking a motorcycle safety course. These are available at many local colleges, and there are also national organisations such as BikeSafe run by the police and FireBike by the fire service.