Instead of removing the carb. I have had them stuck badly when just being unused for long periods of time. I have had success every time in loosening the carb control simply by using WD40 squirted in and letting it work around in it then using pliers to easily but forceably moving the control arm little by little. if barrel is partly open then use a dowel inserted into barrel to help force it to open. If not successful and head of screws are totally messed up. You will have to drill hole in screw and use an easy out.