That "click" you hear with the piston at TDC is normal. Even well broke-in engines will do it. With the top of the cylinder being narrower than the bottom, the piston sticks a little bit and when the conrod switches sides there's a little "dead spot" where the piston doesnt move and thats where the click comes from. My car and airplane engines all do it. If you dont know how much fuel has been in the engine, I'd check the crankpin/conrod for excessive play.