I strongly disagree with John Tuttle about testing of air motors
by closing the suction port and turning the air motor backwards.
It has been our policy for many, many years to not send out an air
motor that shows leakage when tested in that manner.

If everything is tight and the valves are properly set, it is almost
impossible to turn the motor by twisting on the sprocket without
getting dents in your fingers.  This very simple test  can tell
basically which bellows system leaks and whether the valve timing
is correct.  Testing the motor this way is actually testing against
a higher differential pressure than the motor will normally operate.

As far as in-home-repairs, I tell the customer where I think the
leakage is and what repairs would be the most economical.  Nobody
has ever showed us the door until after those repairs were made, if
possible.  If not, it goes to the shop for rebuild.  Customers seem
to appreciate this approach.

Bob Lemon