CHOKE

A butterfly valve or plate located near the top of the carburetor that limits or restricts the amount of air allowed to enter the carburetor , thus enriching the fuel-air mixture and enabling the vehicle to start and run more easily when cold. Automatic chokes have a thermostatic coil or thermostatic spring that activates a butterfly valve at the top of the carburetor barrel . Older cars have manually operated chokes. Some vehicles use an enrichner instead of a choke. Also see automatic choke