WITH THE ROTOR *LOCKED*:

put a 3 ohm reference resistor in series with the RS775.

put a function generator across this series circuit.

set the function generator for ~8000Hz sine wave at ~1 volt peak.

using a digital multimeter on AC setting:
measure voltage drop across the reference resistor,
then measure voltage drop across the motor.

adjust the frequency until the meter reads the same voltage drop 
across the reference resistor as across the motor.

Then calculate inductance as follows:

L = sqrt(Rr^2 - Rm^2)/(2*pi*f)

where:

Rr is the reference resistor ohms (measure this with ohmmeter),

Rm is the motor resistance ohms (measure this with ohmmeter),

f is the frequency (Hz) where the voltage drops are equal