purpose of choke

[PKRWUD]

Iron Skull-
Another pretty easy one. When an engine is cold, the air and fuel don't mix very well because the gas stays in a liquid form, and it's harder for the engine to start. The solution for this is to reduce the amount of air let in, so that the mixture is richer. This will get the engine going, and after a few minutes of running, the engine temp warms up enough to vaporize the fuel/air mixture, thus burning better, with less need for gas. After 5 minutes, the engine is normal, and the regular air fuel mixtrure presented by the carb idle circuit is fine. So, the question the engineers had was "How do we reduce the amount of air going into the engine for the first 5 minutes?". The answer was a choke. A manual choke is one that the driver operates by hand. When the engine is cold, you close the choke. This reduces the air going in, and richens the mixture. As it warms up, you let the choke out. After 5 minutes, the choke should be completely open.

It has nothing at all to do with performance. It is used to "choke" the air supply to the engine in order to warm it up.

Take care,
-Chris