In the context of motorcycles, the reserve mode refers to a secondary fuel supply setting that allows the rider to continue riding when the main fuel supply is running low. Most motorcycles have a fuel tank with a fuel petcock, which is a valve that controls the flow of fuel from the tank to the engine.
Typically, a motorcycle's fuel petcock has two or three positions: On, Off, and sometimes Reserve. When the petcock is set to the On position, fuel flows freely from the tank to the engine. When the fuel level drops to a certain point, indicating that the main fuel supply is running low, the rider can switch the petcock to the Reserve position.
The Reserve position on the petcock opens up an additional fuel outlet in the tank, which is positioned lower than the main fuel outlet. This allows the remaining fuel in the tank, which may not be accessible in the normal On position, to be used. By switching to Reserve mode, the rider can continue riding for a certain distance, providing an opportunity to reach a fuel station for refueling.
It's important for riders to monitor their fuel level and switch to the Reserve mode when necessary. It's also a good practice to refill the tank as soon as possible after switching to the Reserve position to avoid running out of fuel completely.