What does the term 'leaning out the carburetor' mean?

Leaning out the carburetor refers to the process of reducing the amount of fuel in the fuel-air mixture that is delivered to the engine. This action increases the air-to-fuel ratio, making it leaner. When the carburetor is leaned out, there is less fuel relative to the amount of air entering the combustion chamber. This can lead to more efficient combustion and improved fuel economy, especially under certain operating conditions, such as when an engine is running at higher speeds.

It is important to achieve the correct air-fuel mixture for optimal engine performance. Too rich a mixture (more fuel than air) can lead to incomplete combustion, reduced power, and increased emissions. Conversely, leaning out the mixture too much can lead to engine knock and overheating, so it's crucial to find a balance based on the specific engine and operating conditions.