ENGINE
Inspecting the Cylinder Block and Components
12/05
6LY3 Service Manual
5-31
© 2007 Yanmar Marine International
Check Valve Seat Wear and Contact Surface
• Inspect the valve seat for scratches and
excessive wear.
• Check to make sure the contact surface is
normal.
The seat angle must be checked and adjusted if
the valve seat contact surface is smaller than the
width of the valve seat.
NOTICE: The intake and
exhaust valves have different diameters.
Check the Sink of the Valve Seat
Over long periods of use and repeated lapping,
combustion efficiency may drop. Measure the sink
of the valve seat using a depth gauge.
Replace the valve and valve seat if the valve sink
(Figure 5-24, (2))
exceeds the tolerance.
Figure 5-24
Figure 5-24
1 – Cylinder Head
2 – Valve Sink
Check the Valve Guides
Measure the inside diameter of the valve guide and
compare it to the Valve Guide Specifications Chart
below. Replace the valve guide if it exceeds the
wear limit.
NOTICE: The inside diameter standard
dimensions are measured after the guide is
installed in the cylinder head.
Replacing the Valve Guide
Use the valve guide insertion tool
(Figure 5-25, (1))
and tap valve guide
(Figure 5-25, (2))
into the
cylinder head
(Figure 5-25, (3))
.
Figure 5-25
Figure 5-25
1 – Insertion Tool
2 – Tap Valve Guide
3 – Cylinder Head
4 – Tool
Intake Valve Sink
Standard
Limit
0.7-0.9 mm
(0.027-0.035 in.)
1.2 mm
(0.047 in.)
Exhaust Valve Sink
Standard
Limit
1.2-1.4 mm
(0.047-0.055 in.)
1.7 mm
(0.066 in.)
0005605
(1)
(2)
Valve Guide Specifications
Standard
Limit
Valve Guide
Inside
Diameter
Intake
8.010-8.025 mm
(0.3153-0.3159 in.)
8.1 mm
(0.318 in.)
Exhaust
8.015-8.030 mm
(0.3155-0.3161 in.)
8.1 mm
(0.318 in.)
Clearance
Intake
0.035-0.065 mm
(0.0013-0.0025 in.)
0.18 mm
(0.007 in.)
Exhaust
0.045-0.075 mm
(0.0017-0.0029 in.)
0.18 mm
(0.007 in.)
0005606
(1)
(2)
(
3
)
(4)
