So I've got an early 70's Pug UO-8. The fixed cup (drive side) keeps unscrewing during pedaling, and even when it's "tight," it clunks (it's not the cotter - you can feel the other side move up while that side moves down and vice versa). Is there any way to get it REALLY tight without removing the crank? I don't have an adjustable wrench (or any other wrench for that matter) that is big enough to fit, yet narrow enough to get behind the chainrings. Any ideas?