Originally Posted by flypaper 2
Over amping the motors to start with. It's rated for 16 amps and your running 17 and 21. Use props that run the amps just below its amp rating and it'll be happy. If you want to run a bigger prop, go to a lower KV motor. That particular style of motor was one of the first style of brushless motors to come out. Fairly low quality. I ran them fairly early on and found I had to put epoxy inside the bell as they were very out of balance. HK does have some high quality motors at the other end of the scale.
The listed ratings from what I have found through my own testing is often very wrong. I never take whats up on HK's site as gospel. I Test. My mistake was taking it for granted that each motor is roughly the same ( will not do that again ). If the motor is not getting hot then I'm not over amping it. I have 80 plus flights on the first 2 I purchased without an issue. Including a few dirt dives and a mid air into a metal light pole.
My experience as a whole from these hobby parts vendors on the information they publish has not been to great. I don't think they actually test these motors real well and the information they publish is often whats posted from users. Now add variance from sloppy manufacturing and that posted information is useless.
Just another lesson to learn. My new method = TEST EVERYTHING.