jcb JS300 Service Manual page 802

Inspection
Check all parts for wear and/or damage. Renew any
components which do not fall within the wear parameters
Wear Limits
Check
Clearance between piston 121
and cylinder block bore.
Backlash of piston 121 and piston
shoe 122 caulking part (d).
Piston shoe 122 thickness (t).
Assembled height of pressure
plate 123 and spherical bush 113
(H - h).
Brake friction plate 742 thickness.
¶
Sliding Surface Roughness
Part
Piston shoes 122
Shoe plate 124
Cylinder block 111 bores
Valve plate 131
Surfaces needing attention should be lapped to restore the
roughness to within the two limits given in the table.
Note: If the sliding surfaces of pressure plate 123 and/or
spherical bush 113 are damaged, both parts should be
renewed.
E-141
Standard
dimensions
(mm)
0.032
0
6
7
4.0
t
JS09750
Fig 17.
Standard surface roughness
0.8 - Z (Ra=0.2)
0.4 - Z (Ra=0.0)
1.6 - Z (Ra=0.4)
0.8 - Z (Ra=0.2)
below, and dress any sliding surfaces with excessive
roughness.
Recommended
replacement value (mm)
0.062
0.3
5.8
6.5
3.6
9813/5100-1
Section E - Hydraulics
Swing Motor
Dismantling and Assembly
Action Required
Renew piston and/or cylinder block.
Renew piston/piston shoe assembly.
Renew piston shoe.
Renew the pressure plate/spherical
bush set.
Renew friction plate.
h
JS09750
Fig 18.
Surface roughness requiring
modification
3 - Z (Ra=0.8)
3 - Z (Ra=0.8)
12.5 - Z (Ra=3.2)
6.3 - Z (Ra=1.6)
H
E-141