Kohler LH630-775 Service Manual page 138

Section 10
Inspection and Reconditioning
Replacement pistons are available in STD bore size,
0.08 mm (0.003 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. The ring
sets are also available separately. 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 10-9) against the specifications listed
in Section 1.
Figure 10-9. Measuring Piston Ring End Gap.
5. After installing the new top and middle
compression rings on piston, check piston-to-
ring side clearance. Compare findings against the
specifications listed below. If clearance is greater
than specified, a new piston must be used. Refer
to Figure 10-10.
10.10
Figure 10-10. Measuring Piston Ring Side
Clearance.
Install Piston Rings
To install piston rings, proceed as follows:
NOTE: Rings must be installed correctly. Ring
installation instructions are usually included
with new ring sets. Follow instructions
carefully. Use a piston ring expander to
install rings (see Figure 10-11). Install the
bottom (oil control) ring first and the top
compression ring last. Refer to Figure 10-12.
Figure 10-11. Installing Piston Rings With Expander.