The IDA carburetors differ from other model Webers in that the float is retained in the carb body and is not removed with the top cover. Two tools are needed for setting the float level - 1. Needle and seat gauge. 2. Spring retainer. All of the tools are no longer available from Weber. The needle and seat gauge is used to determine Dimension A, which should be 18mm on 3bbl. carburetors (40 & 46 IDA 3C) and 24mm on 2bbl. carburetors (IDA). Retaining the needle and seat gauge and holding the float in this position with the spring, check the distance from the top of the carburetor body to the top of the float. This should be 12.5 - 13mm on 3 bbl. models and 5.5 - 6mm on 2bbl. carbs. If the float level is off, modify the position of tabs (Lc) until they are perpendicular to the axis tab (A), and make sure there are no indentations on the contact surface which might affect the free movement of the needles with the ball (Sf) of the valves (V).