Taking the carb off and cleaning it is no magic, most of the Japanese engines run either Mikuni or Kehin(sp) carbs. Most likely there are 2 screws on the carb, one sets the idle speed, the other sets the idle fuel flow. The one that sets the idle speed with usually be located on top with a semi circular plate attached and the screw is just a stop point. The other is usually located on the side, open it(counterclockwise) about 1/8th of a turn. You will probably notice an immediate difference. I'm betting it's gummed up from leaving old gas in there, stabilizer or not.