i have i turf tiger with 1100 hours on it and i hear a wrapping noise near the rear where the exhaust is. it is in the engine for sure but not a engine bearing. i dont know what it could be in there doing this. anyone else have this problem?? it is a KOHLER 23HP and my oil is changed every 15 to 20 hours all cutting season in PA. they dont have timing chains they have gears so i dont think its that. and it is not in the valve train. someone please help with what it could be. thank you..