If you take the three screws and "spring clip" off the black electric choke housing - you can pull it off and have a look at the "bi-metal" strip inside - an electrically heated spring. One end is rigged with a loop that fits over the operator arm for the choke door etc. Simple gadget.With the three clamp screws loosened (and the loop I just described still engaged with the choke door arm) - engine cold and ignition off - no power to the choke for 10 minutes or so - you can adjust the "cold" choke door setting. That puts the spring back to its "normal" un-heated position.
Cold - Work the throttle open and closed once to release the fast idle cam (more on this in a minute). Turn the black choke spring housing in the clamp until the door is within about a 1/4 inch of closed and tighten the three screws. If you put power (and ground) on the two spade connections of the housing - you can stand there a couple of minutes and watch the choke door slowly open as the spring heats.
After you have run the engine and the choke door has opened wide - and then you let the engine cool without ever retouching the throttle - the fast idle cam will hold the choke door open until you work the throttle once. It will then close the door to your setting point.
On the back side of the electric choke housing is the fast idle cam and the infamous screw that sets fast idle speed. It is nearly impossible to adjust this sucker with the carb on the engine. The designer of this "feature" deserves the name "toaster engineer". Adjusting this screw is "trial and error" in extreme. After each trial the engine has to go cold to re-set. Duh.....