What is the main purpose of the idle circuit in a carburetor?

The main purpose of the idle circuit in a carburetor is to maintain engine speed at idle. At idle, the engine requires a specific air-fuel mixture to run smoothly without stalling. The idle circuit ensures that the engine receives this mixture by providing a steady supply of fuel that is drawn into the airflow at lower throttle positions. This portion of the carburetor bypasses the main jet and acts independently to control the fuel flow when the throttle is closed, allowing the engine to idle consistently at low RPM.

While the other options touch on various functions related to carburetor operation, they do not specifically address the primary role of the idle circuit. The idle circuit is not primarily designed to provide extra fuel during acceleration, regulate fuel temperature, or enhance fuel atomization, as these aspects pertain to different areas of carburetor function and operation.