Yanmar 3TNV Series Service Manual page 186

2) Check of brush movement
If the brush does not move smoothly, inspect the brush holder for bending and the brush holder
sliding surface for dirt. Repair or clean as needed.
3) Check the continuity between the insulated brush holder (positive (+)) and the brush holder base
(negative (-)).
If they are electrically continuous, replace since the holder is grounded.
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9. Starting Motor