if it isnt a cable issue as KC described it may very well be an air leak, air leaks are bad, causes lean condition that will kill the engine if run very much.
if the idle screw fell out it was likely do to you having it out so far the spri g had no tension or very little tension on it, so i agree you eitherneed to make sure throttle cable is adjusted with enough slack so the carb slide can move farther down in carb, or you havean air leak between carb and manifold or between intake and cylinder.