If the engine is indeed new i would probably take it off the plane and set it up on a pc of wood and do some bench running first, maybe spend the extra $5 and get a new tank for your bench running, this way if it runs fine on the bench then you know your problem lies in the tank installed on the plane. All new engines should be broken in first anyways, plus this will give you some experience with the engine before trying to fly a plane with it.