After 170 flights with absolutely no problems, I developed a problem of the engine quiting in flight, not abruptly just winding down to a stop. Feeling it was too rich, I had 2 turns out, I started at 1 and 1/2 and had good success through about 5 flights, now did it again and I've changed plug, move the needle out and back in, and the engine will start but can't keep the low in running and when I move it to high throttle it acts like it want to quit again. I thought about moving the pump screw but ain't got a clue which way or if that will help. Is it outside or inside the engine?