Yeah, all four of mine get almost hot. Not so hot that you cannot touch them but very warm. This is always after long flights of 15 to 20 minutes. I also did some load lifting measurements a few weeks ago and then also noticed them getting very warm. I figured by that experiment that it was not good on the motors to put them under that kind of sustained load for a lengthy period of time. As I added more weight to the hoovering Phantom 4, the prop noise grew louder and louder and the tone or pitch increased. I figured this indicated added stress on the entire power train and body. I also noticed that the fairly short flight (hovering) which lasted maybe 6 or 7 minutes, drained the fully charged battery to about 55%. All this spent energy went into heat for the motors, propelled air, and noise to mention a few. I plan on doing some more testing fairly soon and I will add some additional items to monitor and test and I will add motor temperature to that list! I will also monitor this thread to see how others post about their Phantom motors heating up. Thanks for getting this started!
Jim
WA5TEF