a couple of points worth considering....is the carb sealing properly as any air leaks will cause inconsistencies try changing the o-ring or use a sealer if possible
Also glow engines have no choke so they need a richer fuel mixture to start than when they are warm/hot
also on rotary carbs make sure the throttle is open slightly whilst trying to turn the idle screw as otherwise you are fighting against the servo and can damage the srew end..slide carbs are a lot better...hope this helps a bit