S301G | Here you can talk on other Brands Of Helis Apart from Syma | Syma Forum

Well, first off, the main rotor, when broken off, will cause problems. The 107 at least is very unstable when you break off a rotor tip.

However, since you removed that and it's still doing it, my first guess would be the main shaft. Look that over for bends or kinks, even tiny ones. Set the heli next to something straight up and down (plumb) with the shaft lined up to it. Then slowly turn it to look and see if you see a gap form, get larger, get smaller or dissapear between it and the edge of whatever you use, or if it moves in general. (coffee table leg, a peice of trim on a corner, anything with a 90 degree angle to the floor and the skids)

If there isn't a bend, then check the gears, balance bar, dogbones (the little loops kinda shaped like an infinity symbol or an 8 that attach to the balance bar and top rotors) and reply what it is or isn't. Then we can move on from there.