Still new, and as stated above it is overheating, next time run it a bit richer, you should have a very definite trail of smoke, as soon as you take off, gain as much altitude as possible, throttle back to no more than 3/4 throttle, and do lots of loops and flying around, without changing the throttle setting, see how it does, Saito's are hard engines, they take a little longer than most to brake in, but then, is when you fall in love with them! Use 15 % nitro fuel.