ALOT OF GOOD ANSWERS HERE BUT I DONT SEE ANY ON THE FUEL ITS SELF. WHO OLD IS YOUR FUEL ? WHAT % ARE YOU RUNNING. I ALSO THINK THAT YOU NEEDED TO CHANGE PROP BACK TO 14' AND BY WHAT YOU HAVE TOLD US I THINK THAT YOU ARE RUNNING TO RICH.. HEAD NOT HOT, SMOKE TRAIL, SURE IT MITE BE RUNNING GOOD ON THE GROUND BUT 200' UP IN THE AIR YOU WILL RUN RICHER. LISTEN TO THE MOTOR IS IT RUNNING 2 OR 4 STROKE ? AND AS FOR THE GUY THAT TALK ABOUT THE EXSPANTION WAVE AND OVER REV. GREAT JOB.