2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 357Get this manual
BRAKES 8Remove the slide bolt bushingsInspect the bushings and O-rings and replace if necessarycorrosion, or galling and replace if necessary
O-ring Inspect
Bushing
9Measure the inside diameter of the rear caliperThe caliper body is 2-step pistonThe rear step is measured as well as the outside step11Inspect surface of caliper piston for nicks, scratches, or damage and replace if necessary
Assembly
1Install new O-rings in the slide bolt bushing holesBe sure O-ring and seal grooves are thoroughly cleaned of all residue, or piston may bind in boreApply brake fluid to piston seals and install carefully with twisting motion to ease assembly until fully seated