I have the Superstar .40 trainer ( O.S. Engine) and plan on taking it up tomorrow, and haven't been able to fly it in about a week so I was feeling ancy and decided to crank it up last night...

Fired on the first try then slowly died to idle, and the prop nut came off, so i re-tighened it and put the spinner back on. I had my friend holding the plane from moving while I cranked it and operated the controls, well, I put the glow igniter back on and flipped it over again, and it fired, and started to die, it was at this moment that my friend and I noticed the prop was blowing air FORWARD not backwards like normal, suggesting that the engine was running in reverse. This lasted for about 2 seconds, and then a small kick was felt and it began blasting air backwards like normal again. It's run fine since

The only thing I can think is that it might have had to much pressure when I flipped it, but it still managed to fire, but only when the piston was TDC and pushed it in reverse. Technically I can think of no reason for it to not function like this, but found it very strange..

Any thoughts??