Dears,
I bought a new OS 71 4 stroke to mount it on my Funtana s40, the engine was doing great and the plane was really fast, but suddenly after a couple of weeks (after breaking in) the engine started to lose power and now it barely flies the plane, i tried the high end needle but I couldn't get more power, I'm using cool power 5% fuel, please help me, I don't have enough experience with engines.