10.6
Section 10
Internal Components
Stuck, Broken Rings Abrasive Scratched Rings
Overheated or Deteriorated Oil
Scored Piston and Rings
Figure 10-5. Common Types of Piston and Ring Damage.
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 rings sets are also available
separately for STD, 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 if
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 using a
feeler gauge (see Figure 10-6). Compare findings
against specs below:
Top and Center Compression Ring End Gap
CH11, 12.5, 13, and 14
New Bore .............. 0.3/.05 mm (0.012/0.020 in)
Used Bore (Max.) . 0.77 mm (0.030 in)
CH15, 16
Top Compression Ring End Gap
New Bore.............. 0.2800/0.5100 mm (0.011/0.020 in)
Used Bore (Max.) . 0.79 mm (0.031 in)
Center Compression Ring End Gap
New Bore.............. 0.2200/0.4800 mm (0.0086/0.018 in)
Used Bore (Max.) . 0.76 mm (0.029 in)
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