Wash beans thoroughly. Set aside. In a Dutch oven, fry bacon until crisp; add onions and saute until soft. Add beans, chili powder, cumin, thyme and salt. Cover with water (about 3½ to 4 cups). Cook slowly for 5-6 hours, or until beans are tender. To thicken gravy, spoon out about ½ cup beans, mash with fork and return to pot. Serve hot. These beans freeze well. Makes about 4 cups cooked beans.