Yeah,I didnt listen to anyone when I got my Axial .28 and then I broke it in and tried to tune it, and it had an air leak on the plate behind the pull start. Check it out the o-ring back there was very thin and crappy on mine, that was the culprit. I sealed the whole engine and it runs like a champ with 30%nitro. If it has a bad seal it might be easier for you to find a better o-ring over there for it than finding copper hi-temp sealent.