Kohler Comand Pro CH1000, Service Manual

Page: 106 / 142

Section 9
Inspection and Reconditioning
9.10
Replacement pistons are available in STD bore size,
and in 0.25 mm (0.010 in.), and 0.50 mm (0.020 in.)
oversize. Replacement pistons include new piston ring
sets and new piston pins.
Replacement ring sets are also available separately
for STD, 0.25 mm (0.010 in.), and 0.50 mm (0.020 in.)
oversize 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 scu
ff marks, the old piston may be
reused.
3. Remove the old rings and clean up the 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 the cylinder bore and check the
end gap. See Figure 9-9. Compare the ring gap to
the speci
fi cations listed in Section 1.
Figure 9-9. Measuring Piston Ring End Gap.
5. A ft er installing the new compression (top and
middle) rings on the piston, check the piston-
to-ring side clearance. Compare the clearance
to speci
fi cations listed in Section 1. If the side
clearance is greater than speci fi ed, a new piston
must be used. Refer to Figure 9-10.
Figure 9-10. Measuring Piston Ring Side
Clearance.
Install New Piston Rings
To install new 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 9-11. Install the
bo
tt om (oil control) ring fi rst and the top
compression ring last. Refer to Figure 9-12.
Piston Ring
Piston Ring
Expander
Figure 9-11. Installing Piston Rings.