I found a Japanese clone at Goodwill today. I am new to vintage machines. Should I pick up machines for parts if I really don't know what I am doing or just stay with machines that are in great condition? The machine today was missing the slide plate but the belts looked good and I am concerned about the motor as it seems to have a residue on it. It has the bobbin case and a bobbin. The flywheel moves freely. At 29.99 is it worth it?