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mon-thurs 9-5 cst
The idle mixture screw controls the fuel mixture for the engine to idle. The idle mixture works with the idle speed screw to set the idle engine speed or RPMs. The idle mixture screw allows you to change the low-speed jet for more performance while allowing you to adjust the idle. Many newer carburetors no longer have the idle mixture screw due to EPA regulations. If you are racing the GX390 carburetor uses the ones with an idle mixture screw for the most performance potential.