There is a hard rubber donut between the top of the motor and the
underside of the suction box.  We replace this with a sponge neoprene
donut that is 1/2" thick.  The donut can be attached to both the top
of the motor and the underside of the box with contact cement.  You
may have to put a speed reducer on the motor to lessen the vacuum.
This motor will also become much quieter.

Mark Haas
Dearborn, Michigan