How do I fix a volume pedal with a slippery string?

My volume pedal (Ernie Ball) had a string that wraps around the pot to turn it up or down based on the pedal position. Problem is, the string is too long (or is just stretched out) and doesn't have enough tension to grip the pot when I sweep quickly, and even when I sweep slowly it only goes 40% to 80% instead of 0% to 100%. I just wanted to check in here and see if there's an easy fix for this that I don't know about. Right now I'm thinking something to do with duct tape.

Thanks
-Jim

Ernie ball sells replacement belt kits check out their site. I am sure they don't cost all that much. Why not fix it the right way?

rosin