[Kurt in NJ]

When you took it apart were there any small specs of silver around the armature where the windings connect to the commutator---and on the field coils opposite that area? ---when a starter is forced to wotk too long, under too much load, and with low voltage a lot of heat is built up that can melt the solder ---the silver specks , it is called throwing the solder ---another thing that causes slow cranking is worn bushings ---the armature drags on the field coil pole pieces ---the armature needs to be close but it can't touch, if it is touching there will be marks from rubbing, and if let go too long the heat can damage the insulation causing shorts.

The brush wires for the ground side screw in, the insulated brushes are soldered in to the field coils, to solder those it is best to have at least a 250 watt soldering iron, I usually use a 600 watt iron because it heats the connection very fast with less chance of cooking insulation, I also use it to resolder the windings to the commutator