Yanmar 3TNV88F, Service Manual

Page: 107 / 266

ENGINE
3TNV88F Service Manual 6-23
Cylinder Head
■
Inspection of valve guides
Visually inspect the valve guides for distortions,
scoring or other damage.
Note: Measure the valve guides while they are
installed in the cylinder head.
Use a telescoping gauge and micrometer to
measure the inside diameter at each end of the
valve guide. Measure in three places and 90° apart
(Figure 6-17) . See Intake/Exhaust Valve and Guide
on page 6-4 for the service limit. Replace valve
guides if not within specification.
Figure 6-17
■
Inspection of cylinder head
Cylinder head distortion
Place the cylinder head flat and inverted
(combustion side up) on the bench. Use a straight
edge and a feeler gauge to measure cylinder head
distortion
(Figure 6-18) . Measure diagonally and
along each side. See Cylinder Head on page 6-4
for the service limit.
Figure 6-18
If distortion exceeds the service limit, resurface or
replace the cylinder head. Remove only enough
material to make the cylinder head flat, but do not
remove more than 0.008 in. (0.20 mm).
■
Inspection of intake and exhaust valves
Visually inspect the intake and exhaust valves.
Replace any valves that are obviously discolored,
heavily pitted or otherwise damaged.
Valve stem diameter
Use a micrometer to measure the valve stem
diameter. Measure the valve stem near the
combustion end and near the opposite end
(Figure 6-19, (1)) . See Intake/Exhaust Valve and
Guide on page 6-4 for the service limit.
Figure 6-19
Valve stem bend
Place the valve stem on a flat inspection block or
layout bed. Roll the valve until a gap can be
observed between a portion of the valve stem and
the surface of the block or bed. Use a feeler gauge
to measure the gap
(Figure 6-20) . See
Intake/Exhaust Valve and Guide on page 6-4 for
the service limit.
Figure 6-20
K0001869
K0000192
K0000197
1
K0000199
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