It sounds like Randy Pepe's Orgoblo motor needs a visit to a good
motor rewinding shop.  They can do all the servicing that might be
required.  With the lubrication system described, it is likely to have
sleeve bearings, which might have to be replaced, and perhaps the shaft
might need resurfacing.  Normally such bearings had no seals.  If the
insulation in the junction box is crumbly, the insulation in the
windings might be in worse shape, indicating the need for a complete
rewinding.

The brush holder, and the adjustment (Right or Left rotation, depending
on the position of the brushes) indicates that it is a wound-rotor
motor, costly to rewind and troublesome to maintain.

All this work could be very expensive; 500 dollars or more.  Unless
authenticity is a requirement, it would probably be cheaper to get
a new motor.  If you keep away from el-cheapo Grainger motors, and go
to Reliance, U. S. Motors, or Allen Bradley, where you might find a
replacement that would match the original's performance exactly, and
be just as quiet, for less money.

Incidentally, it is common for the impellers on smaller blowers and
pumps to be screwed to the shaft.  Set screws can come undone due to
vibration, and create imbalance forces.  One of the rituals that is
done in a plant start-up is "motor bumping"; starting the uncoupled
motors briefly to make sure they turn in the correct direction.
Three-phase industrial motors go either way, depending on how the three
leads are connected.  If a pump runs backwards, even briefly, due to a
wiring error, the impeller unscrews, jams itself in the case, and ruins
the whole thing.

Richard Vance