In large saucepan, cover beans with cold water. Bring to boil; turn off heat and let stand one hour. Drain. Meanwhile, in small bowl, combine maple syrup, chili sauce, onion, salt and mustard. Place half of the beans in 8-cup casserole, top with bacon pieces, then remaining beans. Pour in syrup mixture, then boiling water over all. Cover and bake in a preheated 300F oven about 7 to 8 hours, or until beans are very tender and sauce is thickened. Add water during cooking, if required, to keep beans moist.