Wash and pick over the beans, cover with cold water, and soak overnight.
Drain and rinse beans again, place in a large pot, and cover with cold water. Bring to a boil, reduce heat, and simmer for about 45 minutes, or until the skins wrinkle.
Chop and place the onions in the bottom of a bean pot.
Combine beans, syrup, mustard, sugar, and salt and add to pot.
Score the salt pork and place it on top of the beans. Add water to cover.
Cook at 325 degrees F for about 8 hours. Check and add water as needed.
Remove cover for the last hour to brown salt pork.