I have an evolution .46 that came with my Alpha trainer and every now and then it runs backwards I spin the prop to the left if your in front. It will rebound if I drop the throttle. Why does this happen? Is it bad for engine? Any info would be helpful thanks adam

This happens with most engines when they've been overprimed or flooded. It won't harm them and the simple fix is to just keep reducing the amount of prime you give it until you get to the point where it'll start first go every time (in the right direction ).