Mark and disconnect the wires.
Drop the motor.
Remove the pulley [loosen set screw and if no results, then pry up with two WIDE screwdrivers].
Remove both nutd/bolts/star washers.
Never place anything in those slots you arrowed.
Take one of those screwdrivers, and a good place to put it is against the edge of the lower motor shell.
Tap the screwdriver with a small hammer, going around the lower shell. Might be best to place motor in a vice first.
The bottom will come off, leaving the core with the upper shell.
Now you can soak the bearings with plain, additive-free engine oil.
Use nothing but, and soak a few times. There is a hidden wick around each bearing.
Your Dual is very old. You need to bite the bullet, and do the work.