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Carburetor Help

JFS321's Avatar

Join Date: Jun 2007
Posts: 238

07-12-07, 08:07 PM   #1  
Carburetor Help

Can someone please explain in detail the difference in the idle mixture screw and the idle speed screw on a small engine carb? Info is much appreciated.

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oldchevy4x4's Avatar

Join Date: May 2007
Posts: 96

07-12-07, 09:12 PM   #2  
The idle speed screw holds the throttle plate (sometimes called the butterfly) in the venturi open a bit, to keep the engine running. The more it is turned in, the more it holds the plate open and the higher the engine will idle. The idle mixture screw changes the fuel to air ratio at lower RPMs. The farther in you turn that will cause the engine to run lean, the farther out it's turned will cause the engine to run rich.

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