I own and fly a 2300 with no problems on an 18 x 6 or an 18 X 8 prop but I also use a perry pump and a OS "f" plug. It sounds like a fuel draw problem you have. If you are running an aftermarket muffler plug one of the holes as Volfy has stated or get a pump or better yet a fuel regulator. The pre Chinese carb barrels had problems, this has been corrected.