How To Adjust An Air Fuel Mixture Screw

Having the air fuel mixture screw rightly adjusted and positioned in your car or motorcycle can be the difference between having a smooth ride and one less enjoyable. An air fuel mixture screw also called an idle mixture screw is a special screw on an engine’s carburettor that controls how much air mixes with the fuel.

Once the amount of fuel entering your car engine is increased, it becomes paramount that the amount of air entering the engine be properly balanced too. Doing this will increase the revolution per minute (RPM) of your car, which will result in more speed and power.

Your vehicle needs to have the right measure of air fuel entering the engine to make it work effectively. You don’t need to be a rocket scientist to adjust the air fuel mixture screw in your car or motorcycle. Read on to uncover how to adjust your air fuel mixture screw in these DIY steps:

Step One: Warm Up Your Car Engine

The first thing to do is to start your car by putting the key in the ignition or pressing the ignition button. Allow the engine to warm up for about five minutes in its idle position. Always make air fuel mixture screw adjustments with a warm engine and the engine running, so you can listen to how the adjustments affect the engine’s idle speed. Adjusting the air fuel mixture screw on any device with a Carburetor requires that you turn on the engine before you start.

Step Two: Locate The Carburetor

The air filter is attached to the Carburetor, and it is normally round or cone-shaped.  The air filter on a car might be large and round. It usually sits on top of the carburettor. On a motorcycle, the air filter usually comes off the side of the engine and faces the rear of the bike. Depending on the make and model of the vehicle, different carburettors may have multiple, sometimes up to four, air-fuel mixture adjustment screws.

Step Three: Find The Air Fuel Mixture Screw

The air filter screw is usually distinct from other screws on the Carburetor. This screw is usually a flat-headed, slotted, gold-coloured brass screw on the carburettor. Depending on the engine type of your vehicle or motorcycle, the air filter screw is often located on the side of the Carburetor.

Step Four: Tighten The Air Fuel Mixture Screw Until The Engine Begins To Sound Rough

Using a flathead screwdriver, tighten the air filter screw clockwise until the engine’s idle sound begins to sound rough. Tightening the air filter screw will result in a lean air-fuel mixture, and reduces the amount of fuel entering the engine. This reduces the RPM at which the engine idles. If left this way, your car will have less fuel to run efficiently. This will damage your car engine because there is more friction between moving parts and the engine operates at a higher temperature.

Step Five: Loosen The Air Fuel Mixture Screw

Counting the number of rotations you make, turn the air filter screw anticlockwise to loosen the air filter screw until the engine begins to sound irregular i.e revving up. Loosening the air filter screw allows for a rich air-fuel mixture as more fuel flows into the engine. This increases the RPMs at which the engine idles. Leaving the air-filter screw this way implies your engine has more than enough fuel to run efficiently. This will result in your car or motorcycle consuming more fuel than necessary, hence, increasing your daily fuel expenses.

Step Six: Set Your Air Fuel Mixture Screw Mid-Way Between The Irregular And Rough Engine Sound

This step will make you know the perfect setting position for your air fuel mixture screw. Using your flathead screwdriver, turn the air fuel mixture screw approximately in the middle location between where the engine’s idle sounds irregular and rough. This will set the engine at a regular idle speed.

Step Seven: Make Necessary Adjustments

If you are not satisfied with the sound you are hearing, you can turn the screw ½ a turn either clockwise or anticlockwise until the engine’s idle sounds most even and smooth to balance the fuel mixture. This adjustment process is also known as balancing the idle mixture.

CONCLUSION

There you have it. Not satisfied with how your vehicle engine sounds and operates? You can adjust the air-fuel mixture screw by following these DIY steps.