1986-1987 Honda TRX350 FourTrax 4X4, 1987-1989 TRX350D Foreman 4X4 Service Manual, Page 267Get this manual
STARTER SYSTEM Inspect the brushes for damage and measure the brush length SERVICE LIMIT: 5.5 mm (0.22 in) Measure brush spring tension with spring scale SERVICE LIMIT: 740 (26 oz) (1) BRUSH
Inspect the commutator bars for discolorationBars discolored in pairs indicate grounded armature coils; in which case the starter motor must be replaced