I'm guessing that when you say the engine is mounted at 45 degrees, you mean the cylinder is rotated 45 degrees, so the engine isn't upright or on it's side? At least that's what I'm hoping you mean. If that is the case then I can say that the way the engine is mounted, rotation wise, is not important.

What is important is where the crankshaft is pointing in relation to the rest of the airplane. You'll want to aim the engine's crankshaft "down" (in relation to the airframe) a few degress.

The right turning could also be engine thrust, but I'm guessing it's something else. Try adding some downthrust and see how it flys. And check the alignment of the wing and stab as well.