[Yosemite Sam]

If the adjuster turns easily enough while it's apart but will not when it's put together, then you gotta find out where it is binding.

As mentioned earlier the little spacers could be missing, the belt could be too long/worn out putting the adjustment at the end of its travel.

If the adjustment plate doesn't slide up and down easily with the bolts tight and the adjuster loose, I'd start there.

This has got to be a pita if you're doing it out in the cold.

Good luck.