Inspecting The Cylinder Head - Yanmar 6LY3 series Service Manual

ENGINE

Inspecting the Cylinder Head

The cylinder head is subjected to very severe
operating conditions with drastic and repeated
fluctuations of high pressure and high temperature.
Thoroughly remove all the carbon and dirt after
disassembling. Clean the cylinder head surface
and carefully inspect all of the parts.
Inspect the cylinder head for the following
conditions:
1. Check for distortion of the cylinder head mating
surfaces.
• Clean the cylinder head surface.
• Place a straight-edge along each of the four
sides and each diagonal.
• Measure the clearance between the
straight-edge and mating surface with a feeler
gauge.
Cylinder Head Distortion
Standard
0.05 mm
(0.002 in.) or less
Figure 5-15
Figure 5-15
2. Check for cracks in the cylinder combustion
surfaces.
• Remove the fuel injection nozzle, intake and
exhaust valve.
• Check for discoloration or distortion.
• Perform a dye penetrent inspection to check for
any cracks.
5-28
Inspecting the Cylinder Block and Components
Figure 5-16
3. Check the intake and exhaust valve seats.
Wear Limit
0.20 mm
(0.008 in.)
0005597
Figure 5-17
© 2007 Yanmar Marine International
Figure 5-16
Check the surface and width of the valve seats
(Figure 5-17). If the seat width is too wide, or if
the surface is rough, correct to the following
standards:
Seat Angle
Intake
Exhaust
Intake Seat Width
Standard
1.07-1.24 mm
(0.042-0.049 in.)
Exhaust Seat Width
Standard
1.24-1.45 mm
(0.049-0.057 in.)
Figure 5-17
6LY3 Service Manual
0005598
90°
90°
Limit
1.74 mm
(0.069 in.)
Limit
1.94 mm
(0.076 in.)
0005599