Bests & Worsts Reviews from Amazon

These copters are SO MUCH FUN. But the first two that I bought, after a few too many spectacular crashes, developed a crippling problem called the "toilet bowl effect." They lose their gyroscopic stability and start swirling around (as if they are in a flushing toilet bowl) in a way that makes them impossible to control. I googled this problem, and I tried a few things that DIDN'T work (it's not because lubrication is needed, or because the rotor shaft is loose, or because the balance bar is bent or needs to be replaced). The REAL reason for the problem is subtle breakage in a key part of the upper rotor assembly. It's not the balance bar that needs replacing, but a plastic molded part that is a point of common connection for the central rotor shaft, the upper pair of wings, and the balance bar. I've attached a photograph of the part and HOW IT BREAKS. That is, two tiny arms of the piece snap (the two broken parts are shown). It is very difficult to SEE this breakage because it is mostly hidden, but a careful examination will reveal that this break destabilizes the upper rotor assembly. SOLUTION: Buy the "commonly needed" replacement parts. They're just $5 on eBay (you'll get much faster free shipping from U.S. based suppliers on eBay, because the suppliers here on Amazon are all based in China). Make sure you have a small screwdriver set, and get to work. A little bit of silicone spray lubricant (not WD40, because that will attract gunk) can't hurt. Note that because of small variances in part sizes and screw sizes, I found it best to replace as much of the entire upper motor assembly as you can, rather than just this one piece that breaks. Also note that the replacement kits that I got didn't have every single part (namely, missing the horizontal brackets that hold the wings). Now, instead of two duds plus one functional, I have THREE working copters! Hope this helps. (Oh, and I rate this toy 4 stars, and not 5 because of lack of instructions for how to deal with what seems to be a very common and fixable problem.)