Dave I just got this motor back from you, and had 3 flights on it when the motor was in a vertical climb, and just quit. Upon restarting and transitioning to full power it just backfired and quit. It did this at about 8000 RPM. It did this 3 times before I richened the mixture about 1/8 of a turn, and it seemed to fix the problem. My question is ? Do I have a problem, since most motors give an indication of going lean, before they quit. I am very impressed with the power this engine produces, 9100 swinging a 14-8 Zinger. Any ideas as to what could be my problem, or what will happen if this is allowed to continue.