Prevent wear on commutator

Provide more contact with commutator

Ensure proper heat dessipation

Provide ventilation to commutator

Abnormally woem brush

Over running clutch slipping

Faullty ECM circuit

Poor contacting action of ignition

Motor running but too fast

Motor not running no operating sound of magentic switch

Starter motor running too slow

Starter motor running but not cranking

Burnt commutator

Battery discharged

Worn brushes

Worn pinion tip

Provide grip over armature shaft

Avoid the side way movement of armature shaft

Prevent pinion striking fly wheel

Resist wear on the fly wheel