[mickj]

Once the starter motor off the bike it's straight forward to strip but do not let the motor lead terminal turn in the starter body. After you've given it all a good clean try to find a cap off an thin aerosol, hair moose or similar to hold the brushes open while the armature is slid back in. Push the lid in to hold the brushes back, find one very slightly larger than the commutator with the open end facing inwards when you push the armature in it will push the lid off and seat the brushes.