I had the same problem on a new bafang cst motor and didn't get any joy from the supplier.What an awesome reply!!
Thank you!
The squeak on mine is specifically when the motor is freewheeling with no power applied. I've ordered some new tyres today so when they arrive during the week i'll strip it and give it a good clean up.
Any recommendations on grease?
I traced it to being that clutchplate with the 3 plastic cogs on. Take yours out, stick your finger in the middle hole and try turning the rest and you may hear your squeak like I did. I replaced it with one of these -
http://www.greenbikekit.com/accessories/bafang-8fun-spare-parts/bafang-bldc-hub-motor-clutches.html