ORIGINAL: HighPlains
Two turns open on the needle valve is not enough. Caster or not, your engine will never be a top performer after a break in that you described.
OS manual said 1.5 to 2 turns. Luckily (or unluckily?) it didn't run that long. Could that be the problem? Maybe 2 turns is not enough to get '4 stroke operation'? I went as far as 3 turns, but then right back to 2.