Yes more running time is the answer. Do not try a 14 x 8 prop, it is to much prop for this engine, mine handles fine the 13 x 7; 13 x 8 and the 14 x 6. I found that the K series Master Airscrew works fine and because of the lower pitch tends to move the plane less than others at idle. Remember to set the HSNV first then the LSNV and finally adjust again the HSNV.