Yanmar 3TNV82A Service Manual page 180

ENGINE
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 6-54). See
Intake / Exhaust Valve and Guide on page 6-7 for
the service limit.
Figure 6-54
Valve Recession
Note: The valve guides must be installed to
perform this check.
Insert the valves into their original locations and
press them down until they are fully seated. Use a
depth micrometer (Figure 6-55) to measure the
difference between the cylinder head gasket
surface and the combustion surface of each
exhaust and intake valve (Figure 6-56). See
Cylinder Head on page 6-6 for the service limit.
Figure 6-55
Note: 2-Valve cylinder head is shown. 4-Valve
cylinder head is similar.
6-54
Valve Face and Valve Seat
Always check the clearance between the valve and
valve guide before grinding or lapping the valve
seats. See Intake / Exhaust Valve and Guide on
page 6-7 for the service limit. If the clearance
0000199
exceeds the limit, replace the valve and/or valve
guide to bring the clearance within the limit.
Roughness or burrs will cause poor seating of a
valve. Visually inspect the seating surfaces of each
valve and valve seat to determine if lapping or
grinding is needed.
Visually inspect all valves faces and valve seats for
pitting, distortion, cracking, or evidence of
overheating. Usually the valves and valve seats can
be lapped or ground to return them to serviceable
condition. Severely worn or damaged components
will require replacement.
0000193
4-Valve Cylinder Head
0001755
Figure 6-56
TNV DI Service Manual