If you're sure it's dieing rich, about the only think I could think it might be is some trash in your needle and seat. First I would take the low needle out and blow the port out, clean the needle, and reinstall. If this didn't help, then remove the cover on the carb that has the hole in it to get to the needle and seat. Should be the metal cover. Remove diaphragm and gasket and pay attention to the order they are in. Most the time they come off with cover plate, so that's not a problem. With the cover and diaphragm off, you'll see a small needle and fork held in place with a screw. Remove the screw, and you can take the fork and needle out. But be careful, there is a little spring under the fork. These babies like to disappear real easy! In fact, you can loose them just as easy putting it back together as taking it apart. Very small spring. So clean work bench before you start and expect the worst. Check the needle and seat for garbage.