A petcock, also known as a fuel valve or fuel cock, is a device found on many carbureted motorcycles that controls the flow of fuel from the fuel tank to the engine. It is typically located at the bottom of the fuel tank and has different positions, such as ON, OFF, and RES (reserve).
The primary purpose of a petcock is to regulate fuel flow to the carburetor. When set to the "ON" position, fuel is allowed to flow from the tank to the carburetor, providing fuel for normal operation. The "OFF" position stops the fuel flow, which is useful when the motorcycle is not in use or during maintenance. The "RES" position is used when the fuel level is low, allowing access to a small reserve of fuel in the tank to reach the nearest refueling station.
Fuel-injected motorcycles, on the other hand, do not require a petcock. This is because fuel injection systems utilize an electronic fuel pump to deliver fuel from the tank to the injectors. The fuel pump is controlled by the motorcycle's engine control unit (ECU), which regulates the fuel flow based on various engine parameters such as throttle position, engine speed, and temperature.
Fuel-injected motorcycles have a constant supply of fuel from the tank to the injectors, ensuring an appropriate fuel-air mixture for efficient combustion. The ECU continuously monitors and adjusts the fuel delivery based on real-time sensor feedback, providing precise control over the fuel-air mixture and optimizing engine performance.
Since fuel injection systems do not rely on gravity or a simple on/off valve like a petcock, there is no need for a manual fuel flow control device. The fuel flow is regulated electronically, resulting in improved fuel efficiency, smoother operation, and better overall performance.
It's worth noting that not all fuel-injected motorcycles lack a petcock entirely. Some models may still have a petcock for other purposes, such as allowing fuel flow during maintenance or as a reserve option. However, its role in controlling fuel flow to the engine is typically not necessary in fuel-injected systems.