The motor has a 9 tooth sprocket and axe a 38 tooth running on 8mm chain

The 2 GR01's did give good torque but the problem was the pinion gears slipping on the motor shafts.
The scooter motor gives a much simpler setup and I've welded the sprocket to it so no slipping.

On the scooter motor I had the sprocket was simply held on with a nut. I had another one with a belt drive sprocket. I heated that up to break the glue down then it simply drifted off