This Velo Orange blog post links to an excellent and detailed Japanese post on cleaning Retrofriction shifters. Online translators of Japanese, unfortunately, are quite horrible.
Luckily the exploded drawings require little translation.
Adam Hammond Toronto, ON, Canada *
On Tue, Feb 3, 2009 at 10:53 AM, Jack Fortune <email@example.com> wrote:
> My Simplex Retrofriction shifter which has performed flawlessly for
> several years has begun to slip. After my last ride I tightened the
> set screw sufficiently, I thought.
> The shifter felt tight when I started riding this morning, but after
> several miles the looseness returned.
> Is there maintenance that I should do? Should I simply try to tighten
> the set screw even more? Are there any links to an exploded drawing so
> that I can see how the parts fit?
> Jack Fortune
> Eugene, Oregon USA