2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 405Get this manual
ELECTRICAL 3Remove brush plate and brushesMeasure length of brushes and replace if worn past the service limitReplace springs if they are discolored or have inadequate tensionNOTE: The electrical input post must stay with the field coil housing4Inspect surface of commutator for wear or discolorationSee Steps 3-6 of Armature Testing'Brush Inspection 1Measure length of each carbon brushReplace brush assembly when worn to 516" (8 mm) or lessThe brushes must slide freely in their holdersBrush Length
Armature Testing
1Remove armature from starter casingNOTE: Note order of shims on drive end for reassemblyReplace if 2Inspect surface of commutatorexcessively worn or damaged3Using digital multitester, measure the resistance between each of the commutator segmentsThe reading should be .3 ohms or less
Limit 516" (8 mm) Brush Replacement 1Install new carbon brush assembly in the brush housingNOTE: Be sure that the terminal bolt insulating washer is properly seated in the housing, and the tab on the brush plate engages the notch in the brush plate housing4Measure the resistance between each commutator segment and the armature shaftThe reading should be infinite (no continuity)