Many factory valve fabrications I've seen in Autopiano and Standard
valve actions have shown variation in construction.  This suggests that
the factory had trouble making these valves seat easily.  I've likewise
seen many different rebuilding instructions for these secondaries.

Many rebuilders have had trouble with foam seals sold to be installed
inside the metal collars against the valve.  They work for some people,
but I feel those people are just lucky.  I don't trust them.  The ones
I've seen are too thick and stiff.

For valve seals I make little 3/16" leather washers out of pouch
leather, and make sure the center hole is smaller than the valve shaft.
A 2 mm punch will generally do for that hole.  I put one on each side
of the valve and run the collar up to touch, but not compress.

I make a tool to drive the collar by drilling a suitable hole the
appropriate depth in the end of a brass or steel rod of 3/8" diameter
or larger.  The depth of the hole should cause the collar to stop at the
correct place on the shaft, or very close to it.  Better a thousandth
of an inch short than too deep.  A piece of rod 3 inches long will do.

I never move the collar nearest the threaded end of the valve stem as
that collar is a constant reference point.  I hold the valve stem in
a vice that has copper jaws.  These removable jaws are often available
on eBay.

Hope this helps someone.

Tim Gautreaux