I don't understand why you disagree with John Tuttle in this area.
Are we talking about the same post or did I miss something?  You are
very right about an air motor needing to be airtight.  Your testing 
is exactly as I do with my motor rebuilds.  If it doesn't pass this
test, I did something wrong.

As John has described in his last posing on "Satisfy the Customer
with Minimal Repairs" I agree with him in this area.  We are not
talking about a complete rebuild here, we are talking about going
to a customer's home and getting the player working again.  With the
players that I work with, none of the motors would pass our motor
leakage test.  In fact, I have done this test on many players and
some have not had any back pressure at all.  You would think that
the smoothness of the motor would be a big problem here, but it still
ran to the satisfaction of the customer.

When the customer complains that the player is hard to pump, it's
usually because it hasn't been rebuilt in 40-90 years, with hard
pneumatic cloth and/or valve problems.  It seems that a good indicator
of the condition of the player is sometimes found at the air motor.
If this cloth is hard as a rock, then you can almost be sure that the
key pneumatics also need replacing.

It is true that the air motor will operate on very little air when
rebuilt.  If not done right, then this can be a large percent of the
air needed when used with a very well built, air tight stack.  But this
isn't usually the case when used with a 1920's leaky stack.  In this
case a total rebuild is needed.

Pete Knobloch