Buggy,

Does the top rotor spin freely by hand, or when you turn the rotor does it feel like you are turning the motor also? I had a mini heli almost identical to this from harbor freight ( gave me hours and hours of fun for about 40.00$) Any way the one I had, used small pins that connected the rotor to the main shaft. you may have sheared one of these. My replacement was a small drill bit the same size and there was no way it was going to break! It's worth a look. Good luck