I bought a replacement motor on eBay - there are instructions for switching the motor in the group files at the vintagesingersewing group on yahoo.
One thing you might want to try is dripping a couple of drops of Tri-Flow or sewing machine oil down into the top of the motor at the base of the vertical gear, in the seam. Then run your machine as fast as it will go for five minutes. This may loosen up any old dried crud that might be making your motor sluggish.
If that works, save some motor oil and drip one or two drops of motor oil into that seam. It will work much more slowly and dry very slowly, giving you some extra life in the bearings.
A third option is to contact Jenny at sew-classic and see if she can open your motor and clean the bearings and check the brushes for you. I can't remember if she works on these motors or not, but she is a whiz with 201 & model 15 motors.
Getting the motor out might be the trickiest part. It's not hard - it's just more "sticky" sometimes than you expect it to be. Have fun!