Savage 40,

Put the thottle trim all the way up, it controls not only head speed, but pitch of the blades. If you're still having the same problem, it may be time to get a new 10 dollars motor. Motors can last as long as 100 hours of flight or 10. Hmmm, what a difference. Part of the heli world. Expect weird thing to happen.

Dave / Choppersrule