2001 Polaris Sportsman 400-500 DUSE and H.O. Service Manual, Page 329Get this manual
REAR CALIPER REMOVALINSPECTION CONT8Inspect caliper piston bore for scratches, severe corrosion, or galling and replace if necessary9Inspect surface of caliper piston for nicks, scratches, or damage and replace if necessary
REAR CALIPER ASSEMBLY
1Install new O-rings in caliper body (2 piston seals per caliper half)Be sure O-ring grooves are thoroughly cleaned of all residue, or piston may bind in boreApply brake fluid to pistons and install carefully with twisting motion to ease assembly until fully seated2Install new O-rings between caliper halves