Fred F.......i had almost the same problem as you.. Bought the servo motor
& stand from Nick O Sew i am using it on a Consew 227. the motor would go fast
i would turn the switch down, it would slow some what ,but it never did do what a servo
motor was to do.
i fought that motor and did decide to call them and voice my complaint.....
guess what... he said that they had problems with that motor from the factory.
they replaced it with a "sewquiet 4000 reliable". I HAVE HAD NO PROBLENS
AFTER THE SWAP.......
i beleive you have a bad motor..........