Yanmar 6LPA-STP2 Service Manual page 104

ENGINE
Valve Seat Inspection and Servicing
1. Finish the valve seat surface using a 45°
cemented carbide cutter (Figure 5-31, (1)).
Only cut and remove the minimal amount of
metal as necessary for cleaning.
Figure 5-31
Figure 5-31
2. Check the valve seat for poor contact
(Figure 5-32). Apply a light coat of prussian
blue (or white lead) on the valve face. Lightly
press the valve onto the seat, without rotating
the valve.
3. Check the valve face and seat as follows:
• If the color adheres around 360° of the valve
seat, the valve is concentric. If not concentric,
replace the valve.
• If the color adheres around 360° of the valve
seat, the guide and face are concentric. If the
color fails to adhere around 360°, refinish the
valve seat.
• Inspect the valve seat for proper contact width
(Figure 5-31, (1)) and proper location within
the middle of valve face.
5-24
(1)
0004956
© 2007 Yanmar Marine International
Figure 5-32
(1)
Figure 5-32
Contact width:
• Intake valve: 1.4 to 1.8 mm (0.055 to 0.071 in.)
• Exhaust valve: 1.6 to 2.0 mm
(0.063 to 0.079 in.)
If contact is not in the middle of the valve face,
correct the valve seat as follows (Figure 5-33):
• If the seat position on the valve face is too low,
refinish the seat using 25° and 45° cutters.
Figure 5-33
Figure 5-33
1 – 45° Angle
2 – 25° Angle
6LPA Service Manual
Cylinder Head
0004957
(1)
(2)
0004958