Abstract: A side access fill spout and plug for a fluid container, such as for a drive chain housing for motorcycles, has a filler plug with an upper O-ring seated in the top section and exposed axially downward, and a lower O-ring seated on its shaft exposed radially. The cover plate has a fill spout projecting out and up, with a straight line bore and an O-ring locking groove in the wall of the bore spaced from the top edge of the spout so that the upper O-ring is held in compression against the top edge of the spout by the lower O-ring when expanded into the locking groove, holding the plug securely in place. The bore reduces in diameter below the locking groove to provide additional material to the underside of the junction of the spout and the cover plate.