1. Start by warming the engine up to its normal operating temperature.
2. Once the engine is warm, locate the air fuel mixture screw on the carburetor. It is typically a small screw with a slotted head, and it will be located on the bottom of the carburetor body.
3. Use a flathead screwdriver to turn the air fuel mixture screw clockwise until it lightly bottoms out.
4. Once the screw is bottomed out, turn it counterclockwise 2.5 turns. This is a good starting point for the air fuel mixture setting.
5. Start the engine and let it idle for a few minutes.
6. Listen to the engine idle. If the idle is too high, turn the air fuel mixture screw counterclockwise 1/8 of a turn. If the idle is too low, turn the air fuel mixture screw clockwise 1/8 of a turn.
7. Repeat steps 5 and 6 until the idle speed is set to the desired speed.
8. Once the idle speed is set, turn the air fuel mixture screw clockwise until it lightly bottoms out. This will prevent the screw from turning out too far and leaning out the mixture too much.
9. Test ride the motorcycle to ensure the air fuel mixture is set properly. If the motorcycle runs rich, turn the air fuel mixture screw clockwise 1/8 of a turn. If the motorcycle runs lean, turn the air fuel mixture screw counterclockwise 1/8 of a turn.
10. Repeat steps 8 and 9 until the motorcycle runs smoothly at all throttle positions.
Adjusting the air fuel mixture screw is a relatively simple task, but it can make a big difference in the way the motorcycle runs. If you are not sure how to make these adjustments, it is best to take the motorcycle to a qualified mechanic.
