Dears,
I bought a Raptor 30V2 with a Thunder Tiger 39 engine, a Futaba gy240, and a Futaba 2.4 7CH radio. the plane flies good at first but suddenly it starts to turn left (nose left and tail right) by itself and I try to give it a full right rudder but it doesn't respond and keeps turning left until I reduce the throttle then it starts to turn right, also it really is hard to hover because of the engine, it keeps going up and down by itself so I can't keep the altitude steady, I need to know what is wrong with the engine and how to tune it.

I also need to know an approximate number of turns to adjust the low speed needle, I tried to adjust the engine but I couldn't.