T-motor MN505-S 380kv become very hot while running. For reference, it is too hot for lengthy touch. Much hotter than other T-motor motors like U5 etc.
Anyone else experience that with this family of motors? Is it normal?
How many amps are you pushing through the motors?
What size prop?
What voltage?
It just sounds like you have over propped the motors or using too many volts.
I have Quad Tarot X4 (960 Frame) and the same Motors like you running on 2x 6s 10000mah with tmotor Flame 70 A ESCs 18" gemfan-props and my AUW is over 7 kg and after a flight of over 10 min my motors and escs become handwarm but never hot.
What ESC´s are you using like Mike said size of the props and your AUW is important. The highest recommended size for the 505s with 380kv is 18". Size of the power wires from the pdb or lipo to esc and from escs to motors could have an impact to.