Need advice on bottom bracket repair

Hi all,

I have an early 1990s Rodriguez tandem with a rear bottom bracket
in serious need of overhaul. The cranks flop severely.

I've pulled the cranks and the lock ring on the left side, but the
adjustable cup won't come out. It turns about a quarter turn, but
then gets too stiff to turn further. It has no flats for a wrench
instead having holes for turning with a pin spanner--so I'm unable
to put a lot of force on it.

I've soaked it with WD40, but still no joy. Any advice for me?

--
Ted Heise Bloomington, IN, USA