One way to remove a carburetor screw that has been stripped is to notch or cut the head of the screw. This works for screw heads that have been scoured into bowls. To do this, cut a straight line slot into the screw using a very small metal chisel. Cut the slot with straight lines so you can get a flat head screw into the slot. When the slot is cut, just remove the screws with a regular flat head screwdriver. Also, use a decent amount of WD-40 to make sure the screws are lubricated before trying to turn them.
Another method is to remove the screw with a special bit made for stripped screws. These bits sometimes come in a stripped screw removal kit. The bit has a head with teeth on the end that actually grip the screw head. To use it, attach to a drill and place the bit head on the screw head in the scooped out section of the strip. Then drill it into the screw just a little ways. Now, reverse the drill and back the screw head out of the carburetor bowl.
There are other methods available, since removal kits can be expensive. Some carburetor screws are made from very soft metal, so they are pliable and able to be shaped. If you can access the screw head with a pair of vice grips, removal should be very easy. First, lubricate the screw head with WD-40 or Mystery Oil and let it soak for about an hour. Then tighten the vice grips until they close to half the diameter of the screw head. Set the vice grips onto the screw and close them around it. This will compact the screw head and make part of it flush with the vice grips. That should give you enough torque and power to remove the screw.
