Back to trying to help with the carb....
The choke does close all the way. But as far as I understand, a choke closed all the way stalls the engine, so I'm not sure how that would be connected. And yes, the idle screw is almost screwed in all the way. I never touched it. That's just where it lands when the engine idles at about 500 rpms. I have noticed it, though, and think it's a little weird.
I would back that idle speed screw out as shown in the picture I posted earlier. Then set the idle mixture screw by turning it in until it's seated and backing it 1 1/2 turns out. The aim is to set the adjustments back to factory settings. If you cannot get it to idle properly from there, the carb needs a rebuild kit.
