Renewing starter motor

We used to use crocus paper as a final polish of marine industrial generators and exciter armatures many years ago.   But these machines were running 24/7.  The old timers probably still lavish the same care and attention on their classic car dynamo's.

But I don't really think a SD starter motor that has a quick jab a couple of times a week is going to be too fussy.   If you have read all the bumf on DC armatures- you will know that skimming them on a lathe is a pretty drastic move- only if they are very scored or damaged.  Then you have the problem of making sure the insulation bars between them are properly undercut and the original geometry returned.

Just clean it with something like brake cleaner to get rid of all the carbon dust first.   This collects in those gaps between the armature segments and can cause shorting.  It also gets rid of all the oil and grease that has leaked away from the back bearing.  Then just brighten the commutator up with something like very fine 2000 grit Al Oxide paper.   Some people then use Brasso or similar metal polish- but I don't bother.  Final clean with brake cleaner.  Honda FSM describes how to test the insulation and continuity of each bar- but you can usually see and smell if its all fcuked.   Check the condition and length of the brushes- you can get replacements if they are damaged or too short.  The brush springs can break.  All in the Honda FSM.

The motor ends are cast aluminium so clean up well with most things- I prefer vapourblasting but then I would!   The central can is steel, so can be masked off and either rubbed down or dry blasted and re-painted silver.

Biggest failure is that the input terminal is overtightened and spins the internal connections off and/or shorts them out.  Check the terminal is tight in the casing and cannot rotate.