When your bike is good and warm, set your idle screw(Throttle stop?) so that your engine idles at 1100 rpm (+/- 100) and leave it there. No more touching the idle screw
.
The choke cable has an adjustment to help keep the choke lever from sliding down. Directly below your choke knob, but still above the bars, is a rubber cushion with a plastic nut underneath. Pinch this rubber cushion and tighten(clockwise) until there is sufficient drag to keep your choke knob from sliding down.
When you activate the choke you are also causing the accelerator pump to add "extra" fuel to your mix. This helps the cold engine run until it warms up sufficiently. It will also increase rpms. If you get to a stop and your engine is racing try pushing the choke closed and see if that doesn't bring your rpms down.
If you're still having trouble with the choke you can take the gas tank off and check where the cable attaches to the carbs. There is a little "pinch" bolt that holds the choke cable in place. If you don't have the cable "pinched" in the right spot your choke will not operate fully. Too much/ too little choke.
Hope this helps.