I agree with X, you might have an airleak.
Assuming you changed the glo plug and defaulted the needles which you mentioned back to factory settings and that had no adverse effects you might have an airleak.
The tell tell signs of an airleak are overheating, flameout under acceleration and erratic behavior while running.
Did you check to see if the carb was loose?
Make sure the glo plug is tight, and the head bolts are snug as well.