- Commutator
Dirt → Clean with 600 grit sandpaper.
2. Measure:
- Commutator diameter "a"
Out of specification → Replace the starter motor.
Limit 23.5 mm (0.93 in).
![](https://motoinstruction.ru/img/yamaha/20/126680.jpg)
3. Measure:
- Mica undercut "a"
Out of specification → Scrape the mica to the proper measurement with a hacksaw blade that has been grounded to fit the commutator.
Mica undercut (depth) 1.50 mm (0.06 in).
The mica of the commutator must be undercut to ensure proper operation of the commutator.
![](https://motoinstruction.ru/img/yamaha/20/126681.jpg)
4. Measure:
- Armature assembly resistances (commutator and insulation)
Out of specification → Replace the starter motor.
a. Measure the armature assembly resistances with the pocket tester.
Pocket tester 90890-03112.
Analog pocket tester YU-03112-C.
Armature coil:
- Commutator resistance 0.0090-0.0110 Ω at 20°C (68°F).
- Insulation resistance Above 1 MΩ at 20°C (68°F).
b. If any resistance is out of specification, replace the starter motor.
![](https://motoinstruction.ru/img/yamaha/20/126682.jpg)
1. Commutator resistance; 2. Insulation resistance
5. Measure:
- Brush length "a". Out of specification → Replace the brush holder.
Limit 7.19 mm (0.28 in).
![](https://motoinstruction.ru/img/yamaha/20/126683.jpg)
6. Measure:
- Brush spring force. Out of specification → Replace the brush holder.
Brush spring force 5.28-7.92 N (538-808 gf, 19.01-28.51 oz).
![](https://motoinstruction.ru/img/yamaha/20/126684.jpg)
7. Check:
- Gear teeth
Damage/wear → Replace the gear.