I just finished an Ampico rebuild and it danced from the first time
I turned it on.  Now, I didn't really want to drop the box pump out of
the piano, so I kept putting it off.   I finally bit the bullet and
began to seriously study the problem.

As I looked at it, I noticed that the drive pulley, the one on the
electric motor, seemed large.   Back in the early days of rebuilding,
people would occasionally put on a larger pulley, making the pump
turn faster and therefore suck harder.  This helped to overcome small
leaks.  When I totally rebuilt the system and solved the leaks, the
pump now strained and bucked and the piano danced.

Fortunately, I had a couple of other motors with pulleys to compare
and sure enough, too large.  I replaced it with the proper size and,
voila, no dancing!

If I remember right, the original size was 1-3/4 inches outside
diameter, not the 2-1/2 inches as I found on the motor.  A little
observation saved a lot of difficult, wasted work.

Jeff Davis,
Seattle