914 Choke Mechanism

The  "Chokes" on the 900 series engines are technically "Enrichers".
Pulling the Choke/Enricher lever opens an additional fuel passage from the float bowl to the carb throat.
Whereas in a conventional carburetor, the Choke reduces the amount of Air being supplied, the Enricher Increases the amount of fuel, producing the same result.
A quirk of the Enricher is that it only works if the throttle is closed or very near closed (Idle).
As the throttle is opened the vacuum produced by the opening throttle is reduced and the enricher is not able to draw the additional fuel.
This is not a bad thing as it prevents the Enricher from being effective at higher power settings.
if you were to forget to disable the Enricher, your error would have no effect on Takeoff performance.  A Good Thing!

Great explanation here https://electricmotorglider.com/2017/03/01/bing-64-cv-carburetor-starting-carb-part-2/

Mark