The manual that come with my new Thunder Tiger PRO .46 says to bring the piston to near TDC, as in just as the engine starts to meet resistance due to compression, then to attach the prop at 2 o'clock and 8 o'clock positions. I would assume that this is for hand starting purposes, although it doesnt put the prop in the best position for starting. Im using an electric starter anyway. So i dont know. I do know that im not experimenting with it until the warranty period is up on this engine, if i ever do.