(49) . 30. Install pistons (51) and (53) in spool (52) . 31. Install valve (50) , spool (52) , spring retainer (45) , spring (46) , spring retainer (47) and plug (49) in head assembly (3) . Illustration 38 g00833919 32. Install O-ring seal (43) on plug (44) . 33. Install spring (39) , shims (40) , spring retainer (41) , poppet valve (42) and plug (44) in head assembly (3) .