My overlock machine is fixed. It was the motor, which we knew, and after taking it off the table and apart, it was stuffed full of flannel dust. From sewing canton flannel, the loose bits lodged in the back of the motor. Man, there was a lot of it! And a cable was not quite tight enough.
Now it is cleaned out, the cable tightened, the motor back under the table, the machine on top and tried out - it works! Thanks to the help in the building, I'm up and running again.