Check the CARB JOINT. It is a metal tube wrapped in rubber between the engine and the carb (2"X3"). I went out riding and when I came back I had the same problem, would only run on high idle. Sometimes the split in the rubber is real fine, but it allows to much air into the system after everything has mixed in the carb. I have a 01' Warrior and after a few years this is a common problem. Good luck let me know if that was the problem.
White Bros E2