Unless you have the right tools to remove the pole shoes (the steel blocks) it's highly unlikely you'll ever get the field coils out of the housing. The bolts holding them in are extremely tight, and it takes a c-clamp shaped tool called a "pole shoe vise" to remove them. I've rebuilt dozens of starters and generators without taking the field coils out. Just give them a good cleanup with solvent (Varsol or Mineral Spirits) and a blow-dry with an air hose. Don't worry about a little surface rust- - - -it will make no difference whatsoever in the operation of the starter. Pay close attention to the condition of the commutator on the armature, the copper conductors at the end where the brushes ride and the armature windings attach. It should be smooth, with no evidence of burned spots or loose solder joints. Sand it lightly with medium-grit sandpaper to be sure it will make good contact with the brushes.
If the starter needs more work than replacing the brushes and springs, bushings, and possibly a new drive gear, you'll spend more money trying to fix that one than you will on a good rebuilt unit. Field coil replacement and armature repair need to be left to a professional shop with the tools and knowledge to do it right!
Jerry
