What are the causes of a rich air-fuel mixture?

[LeJayden]

The causes of a rich air-fuel mixture are: 1. Damage to the carburetor throttle shaft or gasket; 2. Wet gasoline and excessive carbon deposits on the spark plug electrodes; 3. The choke valve being closed; 4. A dirty or clogged air filter element; 5. Improper adjustment of the float chamber fuel level or a faulty needle valve seal; 6. A clogged air jet or a malfunctioning economizer; 7. Excessive adjustment of the carburetor main jet or significant wear of the main jet. The solutions for a rich air-fuel mixture are: 1. Clean or replace carbon deposits on the ignition coil and spark plugs; 2. Replace the carburetor throttle shaft or gasket; 3. Open the choke valve switch; 4. Clean the air filter element.