Sticking throttle questions

Does anyone know where to order replacement throttle return springs? Mark II enterprises don't carry them. Having a odd issue I assume the springs are getting weak throttle hangs on occasions then other times the pedal moves as it should but does nothing to raise the engine RMP. I have made sure nothing is rubbing then oiled all pivet points and even where to pedal goes through the rubber bushing on the floor. Not sure what's going on any suggestions? And even more confused about the pedal moving and doing nothing

The linkage can get sloppy. There are many places that wear can occur, and it becomes cumulative. There's a 3 position spring bracket. A standard universal throttle spring should work if you stretch it from the proper points. You are pushing on a pedal that may be loose if the teeter-totter linkage that transfers the foot pedal movement to go from a push to a pull on the carb linkage. Those holes can be bored to fit a bigger pin, or better yet, bronze bushings.

You should check your choke housing. The presence of soot means you have a hole in your choke tube in the manifold. It gets sucked into tiny passages in the carb as a tar and can hang up the choke linkage and piston in the mechanism.