A choke valve, also known as a choke plate or enrichment valve, is a component found in the carburetor of many motorcycles. Its primary purpose is to regulate the amount of air entering the engine during cold starting.
When an engine is cold, it requires a richer air-fuel mixture to facilitate easier combustion. The choke valve restricts the airflow through the carburetor, creating a more fuel-rich mixture by reducing the amount of air. This increased fuel concentration helps the engine start and run smoothly when it is cold.
The choke valve is typically controlled by a lever or knob on the motorcycle's handlebars. When the choke is engaged, the valve partially closes, restricting airflow. As the engine warms up, the rider gradually decreases the choke, allowing more air to enter and returning the air-fuel mixture to normal operating conditions.
It's important to note that modern motorcycles often use fuel injection systems instead of carburetors. In such cases, the choke function is usually replaced by an automatic enrichment system controlled by the engine's electronic control unit (ECU) to achieve the same effect during cold starting.