Well before you go cutting anything..

The wiring harness for the carb (four wires as mentioned) has a little green plug. Unplug it. Apply 12v to the power source of the idle solenoid (wire leading to the solenoid that isn't black) and ground out the 2nd black wire. You should hear a click. If you don't the solenoid is bad and needs to be replaced.

If you hear a click, then thats not the cause. Any difference between idling/not idling when engines warm or cold? Even if no, your choke could be out of adjusment and cause this.

Have you played with any of the carb's screws? Test the solenoid and post back.. I'll go into further detail about some other things to try.

Good luck!

Scerb