2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 334Get this manual
BRAKE SYSTEM If necessary, lightly apply compressed air to the caliper fluid inlet to get the piston and dust seal outPlace shop rag under the caliper to cushion the piston when it is expelledDo not bring the air nozzle too close to the inlet or the pistons may be forced out with excessive force that could cause injuryUse the air in short spurtsPISTONDUST SEAL
Be careful not to damage the piston sliding surfacePush the piston seal in and lift it outClean the seal grooves, caliper piston and caliper piston sliding surfaces with clean brake fluid