I’m worried I damaged my new brushless system. It’s a huge power boost compared to the brushed motor I had, but I didn’t realize how hot it was getting until I had run a full pack on it, and it was too hot to touch.
Your motor should be fine. If you didn’t feel its performance drop off during your run, you didn’t damage anything—but, you are correct to be wary of overheating. Avoid raising the motor’s temperature past 170°F; any hotter, and you run the risk of damaging the rotor’s magnets. The good news is, most brushless power systems include thermal overload protection, which will shut the system down if the motor reaches critical temperature. It’s a nice safety feature, but for maximum motor life, you shouldn’t be “thermaling” on every run. Do this: remove the pinion from the motor, and spin the drivetrain by hand to confirm everything is rolling smoothly (if not, troubleshoot and fix). Next, replace the pinion gear with one that’s two or three teeth smaller. This will ease the load on the motor, just like shifting a bicycle into an “easier” gear. An infrared thermometer, also known as a “temp gun,” is a handy tool for RC. Just touch it to the motor to check temperature instantly—much better than the “how long can I touch it without burning myself” method.
The rotor (foreground) is the part of the motor that actually spins. When a motor is overheated, it weakens the rotor’s magnets.
An infrared temperature gauge is the ideal tool for monitoring motor temp. You can get a good unit for under $30.