Problem with brushed staters is they have nowhere for the brush wear residue/dust to go. So the brushes start to stick which increases arcing that increases wear. If you ever need to replace a set of brushes & they are NLA then just go to a car parts place & buy a set. They are all bigger than bike ones, then cut them to shape to fit your starter motor ! Give it a full clean & degrease & all good to go like new again.