Yanmar 3TNV88F Service Manual page 126

ENGINE
1. Clean piston ring grooves using a piston ring
groove cleaning tool. Follow manufacturer's
instructions for correct operation.
2. Wash the pistons in an appropriate solvent
using a soft brush.
3. Visually inspect each piston for cracks. Pay
particular attention to the ring lands between
the piston ring grooves.
4. Measure the diameter of the piston skirt at 90°
to the wrist pin bore as shown (Figure 6-66).
Measurements must be taken at a specified
distance (Figure 6-66, (1)) from the bottom of
the piston, based on engine model. Record the
measurements. See Piston on page 6-7 for
specifications.
Figure 6-66
5. Subtract the piston measurement from the
greatest measurement acquired during cylinder
inspection (see Inspection of cylinder block on
page 6-41) to obtain piston-to-cylinder
clearance. Record the measurements. See
Piston on page 6-7 for specifications.
6. Measure the diameter of the wrist pin bore on
both sides of the piston (Figure 6-67). See
Piston on page 6-7 for specifications. Record
the measurements.
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K0000235
Crankshaft and Camshaft Components
Figure 6-67
7. Measure the outside diameter of the wrist pin in
three places and at 90° (Figure 6-68). See
Piston on page 6-7 for specifications. Record
the measurements.
Figure 6-68
8. Using a micrometer, measure the thickness of
each piston ring. See Piston on page 6-7 for
specifications. Record the measurements.
Note:
• On an engine with low hours, the pistons,
piston rings and cylinders may be reused if they
are found to be within specifications.
• On an engine with high hours, the pistons rings
should be replaced and the cylinder honed
(see Honing and Boring on page 6-46) or
replaced. The piston should be replaced as
necessary.
9. Place each compression piston ring in the
groove as shown (Figure 6-69). Use a feeler
gauge to measure the clearance between the
piston ring and the piston ring land. Record the
measurements. See Piston Ring on page 6-8
for specifications. Replace the piston if not
within specification.
3TNV88F Service Manual
K0000237
K0001889