The ideal fuel/air mixture or ratio for most internal combustion gasoline engines is 14.7 to 1. Meaning 14.7 parts air to one part gasoline. Any ratio below this is considered a rich mixture or too much fuel. Any ratio above this is considered a lean mixture or too much air.
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An engine runs by the combustion of a mixture of oxygen and gasoline. If this mix has too much oxygen, it is said to run lean. When the mixture has too much gasoline in relation to oxygen, it is running rich.
12:1 for rich mixture and it is 15:1 for lean mixture
"Rich" and "lean" refer to the air/fuel mixture. Rich means a higher proportion of fuel than is needed and lean means less. An overly rich mixture can foul plugs, cause sluggish performance and promote carbon buildup in the combustion chambers, as well as decrease fuel economy. An overly lean mixture can cause jerky, hesitant performance, overheating and in extreme cases even melt a piston crown.
51** Fuel System Lean A lean air/fuel mixture has been indicated by an abnormally rich correction factor
Dry is good, but white is bad! It means that the engine is running lean, which will result in the engine running too hot and can cause serious engine damage (even seizure). Below is a guide to reading the spark plug color. Black = Rich. The fuel/air mixture is too rich (too much fuel, not enough air). Tan/Brown = Normal. The fuel/air mixture is correct. White = Lean. The fuel/air mixture is too lean (too much air, not enough fuel).
Turn the idle mixture screw in to lean the mixture, out to richen the mixture.
Your gas/air mixture is too lean. Adjust your carb to be more rich.
A lean mixture is referring to the gas/air ratio. Lean being less gas
to rich of a gas mixture
Lean is a mixture of weed and grey goose!
You didn't mention what kind of carb is on the engine, and that is where you would make adjustments to richen or lean the mixture. Probably best to buy a book on your carb and read it cover to cover.