Bruce Hanover might consider my system which has never failed.  It isn't
fast, but it doesn't have to be, because replacing the tracker bar is one
of the last things I do in a rebuild anyway.  Drop it into a container of
kerosene and leave it for awhile.  The kerosene eventually swells the
rubber, even old brittle stuff.  You can remove the rubber with a broom
after that if you want to.

Craig Brougher

 [ Kerosene (or heating oil or diesel fuel) is far less volatile
 [ than gasoline, hence a much safer solvent, and it should work
 [ equally well upon any of the natural rubbers.  -- Robbie