You likely have an air leak between the carb and the case spigot. Try loosening the carb draw bolt and while pushing down on the carb to compress the "O" ring, tighten the draw bolt. Also, make sure you are closing the carb completely and do not have it stopped partially open. Evo 46 are known for air leaks and running on after shut down. Do a search and you will find more hints. I have a 36, a 46, and a 61 and no problems with them. Good luck