Was the video posted to show that when you cover the idle air bleeds the motor dies?

If so what did that proove? Did the motor die because it was lean, or because it was rich?

If you really want to know, cover the idle air bleeds. When it starts to die, tap on the accelerator pump (squirting a little fuel). If the extra fuel saves it from stalling, that means it's lean. If the extra fuel from tapping on the accel. pump doesn't do anything, it's alredy rich.

This is how I fine tune idle air mixture adjustment too. RPM goes up with a tap, turn the screw out. RPM goes down with a tap, turn the screw in.

The idle air bleed is there to "lean out" the idle main well on the way to the idle mixture screw. By having a "leak" in the "straw" (idle main well) it's pulling on, it mixes air in with the fuel going to the idle air mixture screw adjustment. The reason that it needs this is because the quantiy of fuel needed to idle is very small. It would be very difficult if not impossible to regulate 100% fuel with the screw adjustment. By adding in a significant quantity of air, the mixture screw adjustment is a lot more forgiving.

To clarify... I'm using arbitrary numbers here just for example sake. Lets say the motor takes 1 gallon of fuel per hour to idle. (or 1gph)

Lets say 1 turn of the idle screw will flow 10gph
of fuel.

With 100% fuel (no idle air bleed) being delivered to the idle screw adjustment, you can see right away, that if 1 turn of screw can turn 10 times more fuel then is needed, then you'd be trying to adjust the screw by 1/10th of a turn to get it right! Much to fine of an adjustment...

Now take the case where you have an idle air bleed. Lets say the idle air bleed hole is big enough that most of the work being done by the vacuum is sucking air, and very little fuel. (lets say 90% air, 10% fuel).

Now you can see I still need 1gph of fuel to make it idle. One turn of screw can still flow 10gph of mixture. However now since the mixture being delivered to the back of the idle adjustment screw is so lean (remember only 10% fuel now), it takes much more of a screw turn to get that quantity of fuel in the engine. In this case, since you can flow 10gph with one full screw turn x 10% mixture, you end up with 1gph fuel in the engine. By doing it this way, the mixture screw can be much more finely adjusted.

Hope that makes sense!

LOL... by the way, the motor is rich. Try turning the idle mixture screws almost 100% in, and I bet it idles better...