Needle runs slower than the motor

Question

The needle on my Elna Supermatic just won't catch up to the motor. The motor runs strong and runs according to the pressure on the pedal. The needle won't goes slow if at at all. (It has beautiful stitch though) I took apart the bobbin case and cleaned out the lint, and that helped only slightly. It almost seems like a belt is too big and won't catch and move the needle. Do you know what the problem is and how I can fix it?ThxTerry