We may have found other answers which could help you.
Click here for Engine Revving Upthe thread is bunching on underside of fabric it looks like birdnest?
Presser foot is loose?
What size needles can I use for my Singer 39a3?
how to get the tension right on my machine?
Engine revving up ?
Need a service manual for a Singer Treadle Sewing Machine Model 66-1?