Fig. 119. The Excelsior Carburetor in Which the Air is Regulated by a Ball which Lies in the Tapering Venturi Tube. An Increase of Suction Lifts the Ball and Allows More Air to Pass. ] The purpose of the gasoline strainer is to prevent any water or foreign matter from being carried into the carburetor, and this device should be used on every engine if the owner wishes to be free from carburetor troubles. (112) Installing Gasoline Carburetors. (1) Use brass or copper pipe from the tank to carburetor if possible to avoid trouble from dirt and flakes of rust. (2) When installing a gasoline tank be sure that the bottom of the tank is at least six inches above the carburetor to insure a good flow. (3) The tank should be provided with an air vent hole, or the gasoline will not flow because of the vacuum in the top of the tank. (4) All tanks should be provided with a drain cock at the lowest point so that water and dirt may be easily removed. (5) Clean out the tank thoroughly before filling with gasoline to avoid clogged carburetors. (6) Pipes from the tank to carburetor should never be placed near exhaust pipes or hot surfaces for the gasoline vapor may prevent the feeding of gasoline. (7) Clean out pipes before using. (8) If common threaded pipe joints are used on the gasoline piping, use common soap in place of red lead. (113) Installing the Carburetor. The carburetor should be placed as near to the cylinder as possible, the shorter the pipe, the less the amount of vapor condensed in the manifold. With multi-cylinder engines the carburetor should be so situated, that is, an equal distance from each cylinder, so that each cylinder will inhale an equal amount of vapor. The intake opening of the pipe should be placed near one of the cylinders, or draw warm air off the surface of the exhaust pipe in order that gasoline will evaporate readily in cold weather, and form a uniform mixture at varying temperatures. Great care should be taken to prevent any air leaks in the carburetor, or intake manifold connections, as a small leak will greatly reduce the strength of the mixture and cause irregular running. Always use a gasket between the valves of a flanged connection and keep the bolts tight. If a brazed sheet brass manifold is used, look out for cracks in the brazing. Leaks may be detected in the connections by spurting a little water on the joints, and turning the engine over on the suction stroke. If the water is sucked in the leaks should be repaired at once. Make sure when placing gaskets, that the gasket does not obstruct the opening in the pipe, and that it is securely fastened so that it is not drawn in by the suction. Never allow the carburetor to support any weight, as the shell is easily sprung which will result in leaking needle valves.