Mine did this too. I think it went away (or at least decreased a good deal) when I did the 43T tail upgrade. Seemed like the old belt just didn't quite mesh perfectly with the tail gear causing it to pop out a little bit. I chalked it up to "that's what you get with a belt driven heli for < $200" It's a great little heli for the price but it's not perfect.

Or maybe it is tail blade balance and changing the speed just got it out of it's resonance frequency. The bobble didn't really seem balance related but who knows. Hmm....


I'm more worried about figuring out my cyclic issue. That one still has me stumped.