Fuel reserve
Encyclopedia
In motorcycles and cars, fuel reserve is the extra fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 reserved by the manufacturer in the fuel tank
Fuel tank
A fuel tank is safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine...

 of a car or motorcycle before the main fuel capacity runs out.

In motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s, when the main fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 runs out, the rider
Rider
Rider may refer to:People:* Fremont Rider , American writer and librarian* H. Rider Haggard , British novelist* Rider Strong , American actor, director, producer and screenwriter...

 has to manually turn the reserve knob
Knob
Knob may refer to:* A rounded handle that one pulls or twists:** Doorknob, a round handle one turns to open any door** Control knob, controls a device** Brodie knob on the steering wheel...

, usually located in the left part of the engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

, to the reserve position. This allows the rider to use the remaining fuel.

The purpose of the fuel reserve is to serve as a warning to the rider that fuel is low, as many motorcycles do not have fuel gauges and determining the fuel remaining is difficult. When the main fuel is exhausted, the motor will stop running, prompting the rider to change the position knob to continue riding with a known small quantity of fuel. Often when a rider notices the motor start to sputter, he can access the reserve before the engine shuts down.

In most cases, the main tank and the reserve tank are actually the same tank, but there are two outlets through which the fuel may leave. One outlet is located a short distance above the other. When the fuel selector is not set to the reserve position, the fuel will flow from the upper hole, and will stop flowing when the fuel level gets below the upper hole. When the selector is on reserve, the lower hole will be used, which allows all the fuel to be drawn from the tank.

Because in most cases, the reserve setting simply allows access to all the fuel, rather than a dedicated tank, the reserve selection allows the rider to deplete the main fuel supply as well as the reserve. This causes no harm, except that they may run out of fuel without warning.
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