How Do I Remove A Stock Mix Screw That Is Stuck?
In this lovely film, TJ talks about several methods of removing an Air/Fuel Mix screw that is stuck!
Its worth mentioning something else I forgot to add in this video, you can sometimes use a small butane flame (emphasis on small) to heat the screw and area around it which will typically cause the screw to break loose pretty easily. The rubber O-ring that is on the screw will most likely be toast so be sure to extract all the pieces of it from the carb before putting a new screw in!
Before getting heat ANYWHERE near the carb, remove every single part from the carb that is plastic or rubber such as the diaphragms, gaskets,m floats, all that stuff and then, wrap the carb in a wet towel, except for the mix screw area. this will assist in preventing the heat from spreading to the rest of the carb. take your time and be patient, easy does it!