Syma Forum

There's a few things that can cause this. Pretty simple fix for most of them. 1st, run it at slow speeds, then check the gears to make sure they're running as fast as the others. If they're running slower, it's probably either a gear issue or a blown or defective motor. If that's the case, check over the gears to make sure they aren't missing ANY teeth.

Next, check for gearslip. The upper main shaft is only held down by the gear that it's connected to at the bottom, and can slide up it, causing a loss in grip between the gear and the shaft. Simple fix--just take a small screwdriver or any small flat object that won't bend or break, and gently push up the gear while holding down the rotors.

If that's not it, check the screws in the upper plastic assembly. There's one or two (some have one, some have two) between the balance bar and the assembly that holds the blades. They're directly 180 degrees from eachother, and hold onto a small flat spot in the shaft. If they're tight, good. If not, not good. Also, it might pay to remove them and the assembly, and check that they're lined up with the flat spot in the first place.

Hope this helps!