Setting of the metering lever height for a diaphragm carburetor is one most important adjustment to be made in a diaphragm carburetor. The metering lever’s functionality starts with the atmospheric pressure entering from the vent hole in the metering cover. This atmospheric pressure forces the metering diaphragm assembly down while the low pressure (vacuum) under the metering diaphragm helps to draw it down onto the lever. The lever is depressed, over rides the metering spring and lifts the inlet needle off the inlet seat to allow the fuel mix to enter into the metering chamber of the carburetor. The correct metering lever setting is critical. A lever set too high can cause the metering diaphragm assembly to contact the lever too early and create a rich condition. If the lever is set too low, a lean condition can occur due to the length of travel the metering diaphragm assembly has to make to contact the lever. Our C-1022 Service Manual shows you and walks you through the proper procedure for setting the metering lever height by using the Walbro 500-13 metering lever gauge.