Well, you don't actually grease the motor, you are filling up the motor tubes. You never want grease or oil in the motor rotors. Here is a hint that is in a machine REPAIR manual:
If your motor is running slow and just doesn't have any zip anymore, loosen
the clutch to disengage the needle and step on the gas. Run it at top speed
for a long time until you hear the motor change its sound. Then its run
itself clean. It might take 10 mins, but you will hear the change in the
motor's sound when it's finally cleaned.