In a serviceable carb, the first part of the [cable operated] choke motion moves a linkage that opent the throttle a little. This is the 'fast idle' function & is fully described in the workshop manual.
If the cable is pulled more, then the choke plate is drawn closed progressively to provide enrichment.

Normal idle speed is restored only when the choke knob is pushed fully in again. If this function, which is common to all standard production carburettors, is working normally on your carb, you need only pull the choke knob out a little way to give you the fast idle you need untill the engine warms up a little.