You will need to totally dismantle the motor, arms, crankshaft, etc.
Make sure the cloth on the outside of the slider valves is fully
airtight.  Do not trust the original cloth.  Check the wooden corner
joints as well as these can come loose and leak.  From the pictures
I cannot tell if the cloth is brand new or not.  Coating the inside
of the slider with shellac would not hurt either.

First put a hose end flat over the hole leading to each pneumatic and
blow.  All six pneumatics must be completely airtight.  That being
verified, the whole surface needs to be sanded on glass going with the
grain.  Keep sanding until the whole surface is the same color of wood.

You will notice how uneven this surface is and you may need to start
with coarse sandpaper and once flat sand it gradually finer until you
are sanding it on 320 grit to 400 grit.  You want _all_ the sanding
lines sanded out of the wood so that the whole surface is as totally
flat as you can get it.

Take each slider valve through the same sanding regimen until these
are also totally smooth.  Now you may mix graphite with some methanol
and brush it on the whole surface as well as on the sanded side of the
slider valves. Rub it in (burnish it) with a spare piano hammer.

Now the most important part: re-bush every hole in every arm.  At this
age, we find that every wind motor bushing is sloppy.  I have seen
motors that have been restored once or even twice before and no one
bushed the arms.  This is absolutely necessary for no galloping.  If
you want to check it, hold the crankshaft still and move the arm up
and down.  There must be zero slop in it.

The hinge at the other end is usually bushed and sloppy as well.
The wires to the slider valves will also likely be bushed and sloppy.
Make sure your new felt is tight but not too tight on the crankshaft.
Use bushing felt, not name-board felt or any non-woven felt.

When you have it all back together you can have fun timing it to run
smoothly and quietly, and it will take _very_ little air movement to
run it.

Doug L. Bullock
http://www.thepianoworld.com/