Tim Baxter was commenting on the differences in the sustain pedal
between heavy and light pumping of his 88-note player.

That isn't really "normal." It's understandable how a weak auto sustain
would drop out sooner (and come on less strong) with light pumping than
with heavy pumping, however.  In pianos that are easy to pump
otherwise, but having a marginal sustain pneumatic, single valve, small
bellows, and slow linkage (more leverage), it may be all you will ever
get.

When you are able to pump a piano very, very lightly and still play all
the notes, quite often the auto sustain mechanism will lift so weakly
that only 1/3 to 1/2 of the dampers are really off the strings fully.
Then of course, they return to the strings more quickly.  That is
usually the problem.  So I'd say that Tim is encountering a design
weakness of his particular piano, IF everything else about the piano is
perfect.

However, If Tim were to lift the lid of his piano, reach down
behind the left side of the piano action to the sustain lift rod, and
physically test for lost motion and the evenness of the damper line to
lift together, he may suddenly see what his real problem is --
regulation!

All the damper heads must lift together.  When you just budge the
damper lift rod, you should see every damper in the line budge an equal
amount.  Not too many old uprights with all new dampers are actually
re-regulated to this degree, but they should be.  Sometimes, it is a
problematic combination of ill-adjusted dampers, plus a very
short-throw auto-sustain bellows whose valve travel is too short,
linkage too critical, too much lost motion to begin with, and whose
on/off pedal switch in the trackerbar is half-clogged with grease and
paper dust.

The bottom line is this: If your piano doesn't have a mechanical
problem of some kind, then the operation of the auto-sustain should
be very satisfactory.

Craig Brougher