I think my main motor has died on my dragonfly. The last time it worked I couldn't get it to lift off the ground. I figured I hadn't charged the batteries enough. But since that it only makes that high pitched whine you get as it starts to turn but nothing else.
How do you tell if the motor is really finished and it's not something else?
How long do these motors normally last?

Coltech

It sounds like your motor, strip it down and clean the commutator (where the brushes touch the centre shaft) and use some switch lubricant or WD40 on it. I had mine six month before it went, got another month out of it by cleaning it up!

Steve

What type of motor the 280 serve not for because its power is very marginal change to 370 ( new kit always already equiped with 370 motor) and you should heat sink for both main and tail motor this will keep its life longer. I also have a flight break make the motor cool down by 12v motor fan.

Thanks guys.
Tried cleaning it still no good.
I've now ordered a 280BB motor. (At least I can change the brushes in it.) I've also ordered heatsinks for main & tail motors, plus the alu sleeve and collar for the main shaft.

Not very impressed with the life expectancy of the stock motors. But they do give you a good excuse to upgrade.