Kohler Command PRO CS Service Manual page 123

Replacement pistons are available in STD bore size,
and 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 pistons, and for 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.
The cylinder bore must be deglazed before service
ring sets are used.
Some important points to remember when servicing
piston rings:
1. If the cylinder bore does not need reboring and
the old piston is within wear limits, and free of
score or scuff marks, the old piston may be
reused.
2. Remove old rings and clean up grooves. Never
reuse old rings.
3. Before installing the rings on the piston, place the
top two rings, each in turn, in its running area in
the cylinder bore, and check end gap. See Figure
10-14. This gap should be a maximum of 0.9 mm
(0.035 in.) in a used cylinder bore and 0.2 mm/
0.4 mm (0.008/0.016 in.) in a new cylinder bore.
Figure 10-14. Measuring Piston Ring End Gap.
Internal Components
4. After installing the new rings on the piston, check
piston-to-ring side clearance. Maximum
recommended side clearance is:
Top ring -
0.04/0.08 mm (0.0016/0.0033 in.)
2nd ring -
CS4, CS6: 0.02/0.06 mm (0.0008/0.0024 in.)
CS8.5-12: 0.03/0.07 mm (0.0012/0.0028 in.)
Piston Ring Side Clearance Limit -
0.1 mm (0.004 in.)
If side clearance is greater than specified, a new piston
must be used. Refer to Figure 10-15.
Figure 10-15. Measuring Piston Ring Side
Clearance.
Section 10
10
10.11