There is a air bleed inside the venturi behind the vacuum diaphragm,if you look down inside you will see a small hole cover it with you finger and the diaphragm tube at the same time,it should hold vacuum.On the float level,you will notice the sight plug is higher on the center carb,you can go higher on the ends but will probably have a problem if you go much higher on the center.Just finished this set,sight plug location is very easy to see.
