Dial-A-Matic
As with most vacs start with the basics.On non power drive DAM remove bottom plate,brush & belt,hose between brush & bag,handle & cord assy,bag door.Then go further to the problem area.(Or as one vac guy told me years ago 'Take out every screw you can find and shake it'!) With condition of your motor you might need a parts vac or motor.With some DAMs motor is similar to Portable,Slimline & Swingette.Others will no more.
Good luck