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10.9
Section 10
Inspection and Reconditioning
10
Replacement pistons are available in STD bore size,
0.08 mm (0.03 in.), 0.25 mm (0.010 in.), and 0.50
mm (0.20 in.) oversizes. Replacement pistons include
new piston ring sets and new piston pins. Service
replacement piston ring sets are also available
separately for STD, 0.08 mm (0.03 in.), 0.25 mm
(0.010 in.), and 0.50 mm (0.020 in.) oversized
pistons. Always use new piston rings when installing
pistons. Never reuse old rings.
Some important points to remember when servicing
piston rings:
1. The cylinder bore must be deglazed before
service ring sets are used.
2. If the cylinder bore does not need reboring and if
the old piston is within wear limits and free of
score or scuff marks, the old piston may be
reused.
3. Remove old rings and clean up grooves. Never
reuse old rings.
4. Before installing the new rings on the piston,
place the top two rings, each in turn, in its running
area in cylinder bore and check end gap (see
Figure 10-8) against the listed specifications
below.
Top and Middle Compression Ring End Gap
LV560
New Bore
Top Ring ........... 0.180/0.380 mm (0.0071/0.0150 in.)
Middle Ring ....... 0.180/0.440 mm (0.0071/0.0173 in.)
Used Bore (Max.) 0.76 mm (0.029 in.)
LV625
New Bore
Top Ring ........... 0.180/0.380 mm (0.0071/0.0150 in.)
Middle Ring ....... 0.250/0.450 mm (0.0098/0.0177 in.)
Used Bore (Max.) 0.77 mm (0.030 in.)
LV675
New Bore
Top Ring ........... 0.180/0.430 mm (0.0071/0.0169 in.)
Middle Ring ....... 0.250/0.460 mm (0.0098/0.0181 in.)
Used Bore (Max.) 0.80 mm (0.0315 in.)
Figure 10-8. Measuring Piston Ring End Gap.
5. After installing the new top and middle
compression rings on piston, check piston-to-ring
side clearance. Compare finding against the
specifications listed below. If clearance is greater
than specified, a new piston must be used. Refer
to Figure 10-9.
Top Compression Ring-to-Grove Side Clearance
LV560 .................. 0.040/0.096 mm (0.0015/0.0037 in.)
LV625 .................. 0.040/0.086 mm (0.0015/0.0034 in.)
LV675 .................. 0.050/0.096 mm (0.0019/0.0037 in.)
Middle Compression Ring-to Grove Side Clearance
LV560 .................. 0.030/0.080 mm (0.0012/0.0031 in.)
LV625 .................. 0.040/0.086 mm (0.0015/0.0034 in.)
LV675 .................. 0.030/0.076 mm (0.0012/0.0030 in.)
Figure 10-9. Measuring Piston Ring Side
Clearance.