Originally Posted by efx
I just re-read your post and I had the same problem where the heli would suddenly go up for no reason. That's when I started having the tail belt gear problem. Check to make sure that the small gear that meshes with the main shaft gear is not lose. When mine move up on the shaft, I lose the tail altogether and when it would go back down the heli would just suddenly go straight up or just speed up no matter where or what I was doing. Just use epoxy to keep it in place and that should take care of that problem. My gears have been fine now. The other thing to check after the gear is the tail boom holder. Just make sure it does hold the boom in place. Some just look like they are tight, but they are not. I also had that problem until I took a closer look and fixed it by swapping half of the tail boom from my other 250. Now they both work the way they're supposed to. I keep reminding everyone because these two are the most annoying problems that took me a while to figure out. And the tail rotating. Just put a screw in the middle on that and snug it across the boom through the tail holder. Now both my stock 250s work just fine. Now I'm just working on dialing in all my heli tails to work on both rate and heading hold mode. That takes a while but I got one of my 450's working great now.
Thanks for the input, the tail belt gear problem is one I haven't read about yet. So I've ordered a carbon Align tail tube and an Align tail boom block in hopes they keep the tail tight. I've also ordered some new align ball link things for the ends of my links, I'm hoping they'll work with the existing stock balls better than some of the super loose links that came with my HK FBL head. I dug up a pair of 450 skids that should be a bit more crash resistant than the stockers, I think they'll work well until I get this thing dialed in. Eventually I'll put on some carbon blades after a few steady flights. Between these mods and the kevlar tail belt, I feel like I'm on the right track, and remain open to other recommendations.
All the best!