Flooding, stumble on acceleration and other performance complaints are, in many instances, caused by the presence of dirt, water, or other foreign matter in the carburetor. To aid in diagnosing the cause of the complaint, the carburetor should be carefully removed from the engine without draining the fuel from the bowl. The contents of the fuel bowl may be helpful in determining contamination as the carburetor is disassembled.
Check the fuel in the bowl for contamination by dirt, water, gummy residue, or other material. A magnet moved through the fuel in the bowl will pick up any iron oxide dust that may have caused a blockage in the needle and seat assembly.
Inspect gasketed surfaces between body and air horn, an dbetween body and flange. Small nicks or burrs should be smoothed down to eliminate air or fuel leakage. Be especially particular when inspecting the top surface of the inner wall of the bowl. A poor seal at this location may contribute to ‘cutting-out’ on turns.
Fill the carburetor bowl with clean fuel before installing on the manifold. This will help prevent dirt trapped in the fuel system from being dislodged by the free flow of fuel as the carburetor is primed. The operation of the floats and intake needle and seats may be checked under pressure if a fuel pump is used at the bence to fill the carburetor bowl. Operate the throttle several times and visually check the discharge from the pump jets.
Before installing the carburetor, hold choke valve open and turn the idle speed screw unti it just contacts the throttle lever, then 1/2 of a turn more to open the throttle valves enough to keep the engine running until the idle mixture and final RPM adjustment can be made.