How to Set the Timing on a Carburetor

by Micah McDunnigan
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Most car engines are equipped with what is known as "fuel injection," which puts precise amounts of fuel into the ignition cylinders. Before this technology, all internal combustion engines used devices called "carburetors." Carburetors regulate the flow of fuel into the engine, with the timing settings determining the mix of fuel and air. Carburetors are still used in classic cars, motorcycles and the gas engines for smaller devices such as chainsaws and lawnmowers. While setting the timing on such a device may sound daunting, it is actually easier than it sounds.

Step 1

Turn over the engine. Wait for the engine to warm up to its normal operating temperature, either by letting the engine idle or using the device for a few tasks in the interim — depending on what device the engine is powering.

Step 2

Turn off the engine.

Step 3

Locate the side of your carburetor with one or more screws sticking out. If the carburetor has only one screw, that is the idle speed and mixture adjuster. If it has more than one screw, then each screw will govern the mixture under different engine loads. While carburetors with two screws will frequently have the idle adjustment screw be on the left and the high speed adjustment screw be on the right, this is not a firm rule. Consult your carburetor's manual to determine exactly what each screw governs.

Step 4

Turn the screw whose governing function you wish to adjust clockwise to reduce the fuel in the air-fuel mix being fed into the engine, and turn the screw counterclockwise to increase the fuel in the mixture. Turn over the engine after making your adjustments to see the results of your adjustments on the engine.

Step 5

Repeat the cycle of turning off the engine, adjusting the appropriate function on the carburetor, and turning back on the engine to check the results until you are satisfied with the results.

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