Starter Motor Inspection - 28-MT Series

NOTE: Do not clean the starter motor parts in a degreasing tank. Soaking parts will dissolve the permanent lubrication and may damage the electrical insulation. This will shorten starter motor life.

Clean
Clean all starter motor parts with a clean soft cloth prior to testing.

Inspection of the following steps refer to visual inspection of the starter motor parts and assemblies to determine their serviceability.
1. Inspect all parts for cracks, distortion, or other structural damage. Replace parts or assemblies that are cracked, bent or otherwise damaged.
2. Inspect threaded parts for stripped, crossed, or otherwise damaged threads. Replace the parts with thread damage that cannot be cleaned up using a suitable tap or die. Replace any items that have damaged threads.
3. Inspect the solenoid assembly for cut or torn boot. If the boot is damaged, replace the solenoid assembly.
4. Inspect the clutch drive assembly. Replace the assembly if the following conditions exist:
- The pinion gear turns roughly or turns in both directions
- The pinion gear teeth that are broken or show evidence of step wear
- The shift lever collar shows deep scoring or other damage
5. Inspect the brush holder assembly for loose riveted joints and cracked or broken insulation. Replace it damaged.
6. Inspect the brushes for excessive wear. The minimum allowable brush length is 12 mm (0.472 inch). Replace excessively worn brushes in sets.
7. Inspect the drive end housing bushing for scoring or other damage. Replace the damaged bushing.
8. Inspect the ball bearings in the following way:
- Hold the armature or driveshaft and slowly rotate the outer bearing race by hand
- Check that the bearing turns freely without binding or the feel of flat spots
- Replace damaged bearings
9. Inspect the armature assembly for the following conditions:
- Gear teeth that are broken, or that show evidence of step wear or root interference.
- A rough commutator surface. Polish with 400 grit polishing cloth if necessary. Thoroughly clean metal dusts from between the commutator bars. If the commutator surface cannot be repaired in this manner, replace the armature assembly. Do not turn the commutator in a lathe.
- A worn commutator. Replace the armature assembly if the commutator outer diameter is less than 36 mm (1.378 inch) or if the undercut depth at any point is less than 0.2 mm (0.008 inch). Do not undercut the insulation.
10. Inspect the driveshaft for the following conditions and replace if necessary.
- Scored or damaged shaft where it turns inside the bushing
- Internal gear with teeth broken or showing evidence of step wear
- A damaged spline. The clutch drive assembly must slide smoothly and easily over the full length the spline.