10.11
Section 10
Inspection and Reconditioning
10
Replacement pistons are available in STD bore size,
and 0.25 mm (0.010 in.) oversize. Replacement pistons
include new piston ring sets and new piston pins.
Replacement ring sets are also available separately for
STD, and 0.25 mm (0.010 in.) oversize pistons. Always
use new piston rings when installing pistons. Never
use old rings.
Some important points to remember when servicing
piston rings:
1. The cylinder bore must be de-glazed before
service ring sets are used.
2. If the cylinder bore does not need re-boring and
if the old piston is within wear limits and free
of score or scuff 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 10-13. Compare the ring gap
to the measurements in Section 1, Specifi cations
and Tolerances.
Figure 10-13. Measuring Piston Ring End Gap.
5. A er installing the new compression (top and
middle) rings on the piston, check the piston-
to-ring side clearance. Compare the clearance to
specifi cations listed in Section 1, Specifi cations
and Tolerances. If the side clearance is greater
than specifi ed, a new piston must be used. See
Figure 10-14.
Figure 10-14. Measuring Piston Ring Side
Clearance.
Install New Piston Rings
To install new piston rings, proceed as follows:
NOTE: Rings must be installed correctly. Install the
bo om (oil control) ring fi rst and the top
compression ring last. See Figure 10-15.
2nd Ring
Top Ring
Oil Ring
Figure 10-15. Piston Ring Positions.
Use a piston ring expander to install rings. See
Figure 10-16.
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