Two strokes (4 strokes too) will run fine inverted if the rules of proper installation are followed. Centerline of tank slightly below the spraybar, tank not too big and positioned not too far behind the engine, fuel feed/fill/vent/pressure lines not kinked or leaking, muffler pressure used and engine tuned (not too lean) correctly. I have successfully run 2 stroke engines inverted in model airplanes since I started fooling with them some 40 years ago. If you are having problems, you are doing something wrong or have an engine with other problems.

Terry in LP