Motor turns freely without belts.  But it still hums. 
I checked terminals...black ohms to orange,  white, and yellow; brown to red.  No ohm to case.
I see the centrifugal switch but can't tell for sure I think it is engaged and not locked out to run. Where is the capacitor for this motor..internal?? What about the thermal cutout, would it cause a hum or would it be off or on??
Thanks for your help!  This unit is old over 30 yrs?? I don't know if it is worth reworking...belts, hose etc!
                
 MJG
                
 August 2009