An auto choke, also known as an automatic choke, is a component found in some motorcycles (and other vehicles) that assists in starting and warming up the engine. It is designed to regulate the air-fuel mixture in the carburetor or fuel injection system during the cold starting process.
In older motorcycles with carburetors, the auto choke is a mechanism that adjusts the amount of fuel entering the engine by restricting the airflow. When the engine is cold, it requires a richer fuel mixture to start and run smoothly. The auto choke accomplishes this by partially closing a valve or flap in the carburetor, restricting the airflow and allowing more fuel to enter the engine.
In modern motorcycles with fuel injection systems, the auto choke function is typically integrated into the engine control unit (ECU) or engine management system. The ECU automatically adjusts the air-fuel mixture based on factors such as engine temperature and ambient conditions. During cold starts, the ECU increases the fuel delivery to provide a richer mixture, simulating the function of an auto choke.
The purpose of the auto choke is to simplify the starting process for the rider. It eliminates the need for manual adjustments to the carburetor or throttle when starting a cold engine. As the engine warms up, the auto choke gradually reduces or eliminates the extra fuel, allowing the engine to run with the normal air-fuel mixture.
Once the engine reaches its optimal operating temperature, the auto choke disengages or returns to its default position, allowing the engine to run with the standard air-fuel mixture for efficient performance.
It's worth noting that with the advancements in fuel injection technology, the use of auto chokes has become less common in motorcycles. Many modern motorcycles feature electronic fuel injection systems that automatically adjust the air-fuel mixture based on various sensor inputs, eliminating the need for a separate auto choke mechanism.