Bushing Engines like the LA and FP series have alot of end play in the crankshaft and the crankcase. Lots of thrust play also you will hear the crank ping off the backplate. That is probably the metallic sound you are hearing. How was the propeller balanced, if you balance a propeller correctly you can place the prop in any position and it should not move? If the prop still rotates when placed out of the horizontal and it rotates back down, then you will have to balance the prop hub.

will