Question about vintage Singer/foot pedal
 

Bought a new motor with foot pedal on eBay. Person said it was running well. When I push the foot pedal, the machine just hums until I basically floor it, then it sews. Is that the foot pedal or the machine?

I would try a couple of things:
Take the belt off, then see if the machine spins over easily by hand. If not, clean and lube.
While the belt is off, see how the motor reacts to the pedal. If the motor with no load still does not start turning over slowly as soon as you start the pedal, but just takes off wide open once the pedal is toward the bottom, then I would try a different pedal.

I would look at the foot petal too and see if something is hung up there, maybe some cat hair or dust off the floor.
Hope you find out what is wrong.

If it's the bakelite button pedal it has an adjustment screw inside. It regulate the speed. There's a blog post on the Archaic and the Arcane on how to service these pedals. I can't link to it at the moment, but it's easy to search up.

This video gives you excruciating detail on adjusting/repairing the vintage controllers.

https://www.youtube.com/watch?v=9OC79P3UWXY

You guys are WONDERFUL! Thank you!