[BigV]

Congratulations Beest!

regarding a choke. It works like it sounds. Take your hands a wrap them around your throat. Squeeze. Feel the choke? Yeah. Same thing in a car (motorcycle, generator, lawnmower, whatever). When the engine is cold, it is easier to burn a rich-er mixture of fuel and air. So, the "choke" operates a linkage/valve/butterfly that *reduces* the amount of air that's going into the engine without changing the throttle position. The throttle controls the fuel (generally speaking), so by reducing the relative amount of air the engine's getting, the mixture has more fuel per air and is therefore richer and therefore ignites more easily.

As the engine warms up, this rich mixture makes the engine run poorly, so the choke is "turned off" as it were. The regular mixture of fuel and air is now restored, and the engine's at normal operating temperature and it runs normally.

eta:
I learned via a google search that adding more gas via a separate line or any other method is still called "choke". The same purpose is achieved, a richer mixture for cold operation.