Clinton Gray suggests his air motor needed only a cleaning, but
there still is a problem -- it don't work!  Can I suggest that
there is only _one_ way to check an air motor, and that is

1. disconnect the drive chain,
2. disconnect the vacuum supply hose,
3. block off the supply port, and
4. try to turn the motor in the 'opposite to normal' direction.

If the motor can be turned, then it requires a complete rebuild.
If the motor cannot be turned, then it is okay.  It's as easy,
and as definite, as that!

Paul Rumpf
Melbourne, Australia