It may be worth noting, that most brushless motors, regardless of setup, will run warm to hot during use. If you can't keep your finger on the motor for more than 2 seconds, it's too hot. If you've got a heatsink, don't touch the heatsink to guage motor temperature, touch the motor it's self if possible. The purpose of the heatsink is to draw the heat away from the motor can. If the heatsink is hot, it's doing it's job. The motor it's self should only be warm to moderately hot. If your ESC and batteries are getting hot along with your motor, then you're pulling to much power. If it's just your motor that's running hot, it probably just naturally runs hot. More efficent motors will run cooler than less efficent (cheaper) motors will. Some brushless motors even have built in cooling fans and/or fins to aid in combating heat. At any rate, most setups will run hot after prolonged flight. Unless the motor is scorchingly hot, I wouldn't worry to much about it.