I have a 2013 Cub Cadet Volunteer 4 x 4 (Model 37BM46GD710) with a total of 235 hours. Engine is a 31 HP Kohler Aegis EFI engine. Yesterday, I filled the tank up with fresh fuel (gas). Today after putting 30-45 minutes on the engine since I added fuel, the engine started sounding funny, more...