Hello Sam,
A lot will depend on the make and model of the machine and whether or not the motor is on the inside or outside, when you release the stop motion to wind a bobbin does the motor run really fast or is it still slow, let me know the details above, you can email me if you want, type in my address as you say it not as you see it.
Ken
drivewithken at blueyonder dot co dot uk
January 2010