You are referring to a nipple to the left of the carb? That's the tank vent. Get a piece of fuel one about 2" long then find two short (3/8 - 1/2") or one long screw (3/4 - 1") with fry fine thread. If you have two pieces, put one half way up the line and one at the top end and mount it on the nipple. If you have one long one, just thread it in the top end. Done.