Besides a replacement plastic cap connecting the "choke" cable to the carburetor, a metal version is available from Stead Engineering. The rubber boot on the cable at the carb helps to seal the system from external air; good idea to snug things down if you can.
The starting enricher ("choke") system acts as a sort of mini-carburetor. When ON, the enricher plunger is pulled from its recess in the carburetor, allowing fuel to enter the venturi; simultaneously, an air passage is uncovered. Thus, the starting enricher system mixes both fuel and air and presents this fuel-rich mixture to the engine for start-up.
After the engine is warm, when idling, a mere jiggling of the "choke" likely will kill the engine.