Yanmar 3TNV82A Service Manual page 181

4-Valve Cylinder Head
Coat the valve seat with a thin coat of bluing
compound. Install the valve and rotate to distribute
bluing onto the valve face. The contact pattern
should be approximately centered on the valve face
(Figure 6-57, (1)) and even in width.
Figure 6-57
Also visually inspect the valve seat for even
contact.
Light cutting can be performed by the use of a
hand-operated cutter (Figure 6-58).
(1)
150°
40°
Figure 6-58
Valve seat diameter can be adjusted by top-
grinding with a 150° stone to make the seat
diameter smaller, and bottom-grinding using a 40°
stone to make the seat diameter larger. Once the
seat location has been corrected, grind and lap the
seat angle (Figure 6-58, (1)) to specification. See
Cylinder Head on page 6-6 for specifications.
TNV DI Service Manual
(1)
0001691B
(3)
(2)
0001862
Grind the valve face and/or valve seat as necessary
to return them to serviceable condition. Grinding is
needed if the valve and valve seat do not contact
correctly. Check the valve margin and valve
recession after grinding.
If the valve or seat require grinding, lap the valve
after grinding. Lap the valve face to the valve seat
using a mixture of valve lapping compound and
engine oil.
Be sure to thoroughly wash all parts to remove all
grinding powder or compound.
Inspection of Valve Springs
Inspect the valve springs. If damage or corrosion is
seen, or if measurements exceed the specified
limits, replace the springs.
Fractures
Check for fractures on the inside and outside
portions of the springs. If the valve spring is
fractured, replace the valve spring.
Corrosion
Check for corrosion of spring material caused by
oxidation.
Squareness
Use a flat surface and a square to check each
spring for squareness (Figure 6-59). See Valve
Spring on page 6-9 for the service limit.
Figure 6-59
ENGINE
0000201
6-55