Sprinkle spareribs with salt. Tie pickling spice in cheesecloth and set aside. In a medium saucepan cook onion in oil until tender, about 3-4 minutes. Add cheesecloth packet, syrup, vinegar, water, mustard and pepper; simmer 20 minutes. Remove cheesecloth. Prepare medium banked fire in covered kettle-style grill. Grill ribs over indirect heat 1 1/2-2 hours, until tender. During last 5 minutes of grilling, brush ribs occasionally with maple glaze, turning to glaze evenly.