Sounds like a similar problem I had on an 05 Ranger.  First thing is CHANGE THE TRANSMISSION FLUID with Polaris AGL synthetic gearcase lubricant, my unit takes 15.2 oz, checking the fluid level is good but will not solve this problem.  Then check the throttle cable at the idle adjustment under the seat, loosen the set nut and slowly turn the idle adjustment until the engine stops, turn the adjustment back about one turn and restart the engine, slowly turn the idle adjustment until the engine barely idles without killing.  If the engine does not stop with the idle adjustment, the throttle stop adjustment nut (just below the black cover on the right side of the carb) is set too high, adjust by slowly turning the nut counter clockwise until the engine stops.