Originally Posted by Nathan Wilson
where would you measure on the motor?
Across the terminals, A, B, and C. That will give you three numbers:
A to B
A to C
B to C
I use an average of these three numbers, and compare it to the average of another motor measured with the same test equipment. As you have mentioned, lower resistance = more power.
The motor can remain connected to the ESC, since the stator has a much lower resistance than the ESC MOSFETs have in their "off" state. Make sure the battery is unplugged!
Use a thermometer to determine the motor temperature during the resistance measurement, then correct the resistance reading back to a reference temperature (traditionally 20C or 25C). (An infrared thermometer, like that used to check maximum motor temperature when setting gear ratios, will do nicely.) The correction factor I use is -0.393% per degree C.