To fix the cable issue you are experiencing, you want to make the outer housing longer in comparison to the inner wire. Turn the adjusters away from the carburetor top on the carburetor end and lengthen the other adjuster on the throttle hand grip. Tighten but do not crank down hard on the locking nuts to hold the adjusters in their new positions.
The threads can be damaged or the adjusters snap in half if the lock nuts are over tightened.
Rich and lean refer to the amount of fuel the carburetor adds to the incoming air.
Heavy or light ratio refers to the amount of oil you add to the gasoline to make the fuel.
If you added 2 ounces extra to the gasoline you have a heavy fuel mix.
Most all of the kit carburetors come from the factory tuned to run rich.
The good news here is your kit came with an NT carburetor, the easiest of them all to work on.
If your spark plug is black and dark it is a sign that the carburetor is tuned too rich. The spark plug color should be anywhere from a cardboard brown to a light chocolate brown color.
Lighter, nearly white color means too lean, not enough fuel. A too lean of a state of tune can do catastrophic damage in a very short time.
Care must be taken when tuning a carburetor to insure that the engine stays healthy. Do this by checking the color of the spark plug frequently while performing the tuning process. Never remove the spark plug while the engine is hot though. Doing so can ruin the threads inside the cylinder head.
Start be raising the clip on the slide needle to the second groove from the top. This will lower the needle further into the needle jet and reduce (lean out) the flow of fuel from just off idle to 3/4 throttle. If you still experience a rich condition past 3/4 throttle you will need to solder the fuel jet closed and drill a smaller fuel metering hole in it.
Just to keep things simple, remember that tuning is done by throttle position more so than engine speed.
Here is the greatest tutorial ever for your carburetor for learning what the parts are and how to care for them, shared for us all by Norman, Lord Vader.
In post #5 he shows the slide, jet needle, circlip.
http://motorbicycling.com/showthread.php?t=302
The whole post will help you out alot in properly tuning the carburetor, but does not cover all aspects of tuning.
If anything seems sketchy, do not hesitate to ask more questions.
Oh yeah, My what a large fuel filter you have there. At least you have it installed in the correct direction. Win!