So an engine will run either way, clockwise or counter clockwise. So is there a correct direction or is it which ever way the prop won't unscrew during run time? [/B]
Modern engines may idle either way, but they won't run well backwards. In fact, many times, if my engines start backwards, giving them more gas causes them to reverse direction. Which gives me an idea...
Is it possible you reassembled the engine wrong somewhere? The direction the engine runs well is based on its timing. Since there are no valves, the timing is dependent on the physical configuration of the ports (the various exhaust and intake openings). I'm no expert, and I'm really guessing here, but it seems if you put some of the parts together wrong, you could have a backwards running engine. For example, if you put the cylinder on so the muffler was on the other side (but I'm sure you didn't do that!)