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Background
A carburetor has mechanisms or circuits that dictate the speed of air flow, and therefore create a pressure that determines the amount of fuel sucked into the air stream. These circuits are called jets. Jets cause the fuel to vaporize as it goes through the large hole in the middle of the carburetor. This hole is called the venturi. The valve on the carburetor called the throttle determines which jets are activated. Different jets are controlled by the throttle opening. The idle jet system is the system that controls 0 to 25 percent of the throttle opening. The jet needle controls 15 to 80 percent. The main jet controls 60 to 100 percent. The jets are designed to overlap each other and are interconnected.
Function
The pilot air jet forms part of the idle jet system. Air pilot jet is a type of the air metering system or air bleeding system. The air pilot jet regulates the amount of pressurized air drawn into the pilot system. This air pilot jet corrects the air and fuel mixture ratio. It improves fuel atomization, which is the process of turning fuel into gas.
Adjustments
Air pilot jets are usually already preadjusted upon purchase of a carburetor. However, engine owners do make adjustments on the jet systems to maximize engine performance, especially on old or frequently used carburetors. If the air pilot jet screw is turned in, it reduces the amount of air, making the mixture richer. If the screw is turned out, it increases the flow of air into the pilot system. The size of the air pilot jet also determines the amount of air that passes through it.
Consequences
If the carburetor mixes more fuel than air then it is classified as a rich mixture. When the amount of air exceeds the amount of fuel, then such a mixture is considered lean. Both types of mixtures lead to the engine`s loss of power. An excessively lean mixture can cause engine damage. When the air pilot jet is not adjusted properly, it can lessen or increase the flow of air, which could lead to extreme mixtures.
Maintenance
A pilot air jet is such a small part of the carburetor that it can be neglected. Cleaning the pilot air jet is very important to avoid any clogging that disrupts air flow. You can remove the pilot air jet using a flathead screwdriver. Remember that the screw is calibrated for performance, so you have to make sure that when you remove the screw, it should be screwed with the same number of turns. You can clean the pilot screw hole using a special carburetor cleaner. You can also spray and wipe off the pilot air jet screw and spring.