Assuming you have a Weber Marelli L1 / L6 / L8 ecu, the CO pot only has 2 turns of + or - adjustment from its zero setting, if you turn it more than that it doesn't do anything. To get back to this setting, turn the screw 5 times in either direction, then turn it the opposite way 2 turns exactley, you now have upto 2 turns of adjustment in either direction.