Ok, so I'm a co owner of a hobby shop, I fly T-Rex's of all size's, Raptor's, etc. I have a little knowledge. Here's my set up...
Hyperion Z3025-10 on stock Sonix 60A ESC
E-Flite Power 25 on stock Sonix 60A ESC
E-Flite Power 25 on Great Planes 45A Electrifly
Stock 24T pinion. I'm notorious for a tight belt. I've had many people look at this, all who criticize my belt tension and they say it's fine. Gear mesh is perfect. The Hyperion motor would grind around half throttle and you would see the windings rattle around in the can. I sent it back for replacement. Second motor did the same. With it not meshed on the main gear it would get to 140 degrees and once the rattle came in it would jump to 180 in about 10 seconds. That was when I put the E-Flite motor back in with the GP ESC...thinking the Sonix was defective and maybe part of it was that is was just bad and was trying to engage the brake at half throttle. (It makes no sense I know but the noise was wierd.)
In the windind on all setups the temp was 220+ and the side of the can was around 190-200.
Someone PLEASE restore my faith in inexpensive off brand heli's...seems like a good product but I'm about to go Align exclusive. I know I get what I pay for but an issue here and there is one thing...like the elevator bellcrank not giving enough travel on the swash (bad geometry, fixed with ATV's), but there is no way I can fly this with it getting this hot.