My panterra scooter has a defective freewheel unit. See picture for the replacement part. How do I take off the old one? Is it threaded on the hub? It looks like it has 2 dimples 180 degrees apart on the face that act as a place to put in a removal tool to unscrew the unit. I fabricated a toollast night and turned the unit counterclockwise but it wouldn't budge. Any suggestions?