Position the piece of hacksaw blade so it cuts on the pull stroke. That makes it easier to control. I use 600 grit carborundum (wet-or-dry) paper to polish the commutator, then clean the mica separators. If there is a bad contact with the brush cables, current through the brush springs can overheat them and make them loose tension. Cranking with a weak battery or excessive cranking will over heat The starter, melting the solder holding the wires to the contacts. A stalled starter will draw 200 amps. If confronted with a weak battery, starting effort will be reduced 40% by pulling out the starter rope 6 or 8 inches to activate the compression release. The upper bearing tends to ware on one side, turning it 180 degrees on reassembly will extend his life. . . 😉
