I'm totally new to RC Helicopters. Bought my 16 year old a U810 for Christmas to see if he had interest. Unit worked well for a spell, but after a ceiling strike (among other crashes) unit won't fly. It wont lift and spins the entire unit on the floor. Looking it over, it appears the top rotor is spinning slower than the lower rotor. Tore it down, but apart from a slight misalignment in the gears, nothing obvious. Thought I felt some binding, but that is cleared up now. Thought we had it figured out, but no joy.
Other Ideas? I'm not thinking it would be too smart to jump straight into lubricating as this unit hasn't flown much yet, but not sure what else to pursue. No obvious bent parts.