These motors have very little torque. It sounds to me like the
armature is binding in the bearings. Sometimes the oil used to
lubricate the bearings oxidizes or burns and forms 'varnish' on
the shaft. I suggest that you completely strip the motor and
make sure the steel shaft of the armature where it runs on the
bearings is clean. If you have the brown staining on the shaft
try removing it with a solvent, but be careful not to get it on
the windings. Some solvents will remove the varnish that
insulates the windings. You can also 'polish' the shaft with
very fine steel wool or 600 or finer paper. It's been a long
time since I have one apart, but you can take them apart.
The other possiblity is the armature is dragging against the
field coils because they aren't lined up correctly.
As for grease, I would use the lightest material you can. Any
heavy stuff will definately slow down the motor.
The shaft which runs through the windshield can also get
corroded, or let water into the motor. The sealing system on the
front of the windshield is not real effective. Make sure that
the seals are in good shape.
Blake
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