Originally Posted by 8gv
The air travels through the crack rather than raising the diaphragm to enrichen the mixture.
"Not exactly," 8gv!
The "choke" (starting enricher) has nothing to do with the diaphragm; rather, when ON, the enricher plunger is withdrawn from its orifice in the carb body, permitting fuel to flow; simultaneously, a proximate air passage is opened. Acting as a "mini-carburetor," the consequent fuel-rich mixture is admitted directly into the carburetor venturi, without involving the diaphragm at all.
A metal "choke" cable cap is available from Stead Engineering. A good primer on a carb very similar to your CVK34 can be found here: