Ok. Finally got the patent images to come up. Adjustment is pretty
simple and explained in the text if you can wade through it. Turning
ring #26 in the patent the direction of the dotted arrow on page two
tightens the clutch. Going the other way loosens the clutch. It's
being held by spring wires #40 on the grooves on the outside of ring
#26.

Further, I see nothing in this that gives an over-center motion,
so I propose you look at the linkage that slides the collar for
this. Maybe the clutch has been overtightened so that the
handle does not reach the over-center part of its action? Does
it feel like the handle is hitting a hard stop or does it just keep
engaging the clutch harder? Since the adjustment is different
for both directions, see if one direction will engage and the
other not, this might tell you more on where to look.

Also, it's possible that as the mechanism wears in a little from
being unused that the disk packs will free up/deglaze/whatever
and the clutch will work a little more correctly. All conjecture
of course, and not worth anything more than what you paid for
it...

--Glenn Lyford