Too rich/lean?

Clockwise to close. Counter to open. At full throttle, point the nose of the plane in the air. If the engine sags, it is too lean. At full throttle, pinch the fuel line. If it dies immediately, too lean. It should speed up a bit before quitting. You can also use a tach. Find max rpm then richen 200-300 rpm. I usually do my adjustments with the tank half full and the engine good and warmed up. That way, it won't lean out in the air when the tank starts to empty.

John VB

You are correct on how to turn the needle valve. A common way to check carb adjustment is to hold the plane with the throttle wide open horizontally and then turn the plane vertical. A properly adjusted engine will speed up slightly when the nose is held up. If it slows down or quits, it's too lean. To check the low end, do the "pinch test". Pinch the fuel line briefly with the engine at idle. If it slows down, the low speed needle is too lean. If it speeds up significantly, it's too rich. A proper setting will give you a slight speed-up. There are two different carbs on model engines, air bleed and twin needle. Look for a small hole in the front of the carb body. If there is one, it's an air bleed type. There's a screw in the side that when turned in blocks the hole. Turn the screw in to richen the idle. Twin needles work the opposite. Turning the idle screw in will lean the idle.

Little engines can be somewhat difficult because they can cool off to the point the fuel won't vaporize, and the engine quits. However, this engine would be great for something like a Dynaflite Butterfly.

Morris

Too lean, the engine won't run well for long, because it'll overheat. Too rich, the engine will sound rough and spew quite a bit of smoke.

Start with the valve about 2 turns open. Close it by turning clockwise to adjust. When adjusting, you can hear the engine RPMs "peak out" as you close the needle valve. After that point, the engine will slow down a little and/or cut out as you close the needle further. You want to be a little on the rich side of that peak point. How much is "a little?" Depends. Depends on the engine, the atmospheric conditions, and the fuel. There's no set number of "clicks" or portions of a turn that works in every situation.

From peak, back it off toward rich until you hear a slight drop in RPM. That should be okay in and of itself, but you should test to make sure. Rev the engine up full throttle, and leave it there. Either pick the plane up and point the nose straight up in the air, or give the fuel line a quick pinch. You are listening for a SLIGHT increase in RPM when you do either of these. If the engine sags, this means you're still to lean. If the engine RPMs go up signifigantly, this means you're a little too rich.

Yes, that is correct.

Most modern engines have downloadable instruction manuals. You might consider downloading the one for your engine, or a similar engine, and reading it.