Wash and remove any foreign matter from the beans. In a Dutch oven, combine beans, water and salt. Bring to a boil; reduce to a simmer and cook, covered, until tender (about 1 1/2 hours). Remove from heat; drain beans and reserve 2 cups of bean liquid. In a casserole or bean pot, combine beans, bean liquid, onion, mustard, brown sugar, maple syrup and black pepper. Top with chopped bacon. Cover and bake in preheated 350 F oven for 2 hours. Remove cover; increase oven to 425 F. Bake until bacon becomes crisp (20-30 minutes longer). Remove from oven and let stand 15 minutes before serving.