Yanmar 3JH3E - 2-1 Inspecting the cylinder head

Chapter 2 Basic Engine
_2._C_y_J_in_d_e_r_H_e_a_d _________________________ 3,4JH3(B)(C)E
2-1 Inspecting the cylinder head
The cylinder head is subjected to very severe operating
conditions with repeated high pressure, high temperature
and cooling. Thoroughly remove all the carbon and dirt
after disassembly and carefully inspect all parts.
2- 1.1 Distortion of the combustion surface
Carefully check for cylinder head distortion as this leads to
gasket damage and compression leaks.
(1} Clean the cylinder head surface.
(2) Place a
straight-edge along each of the four sides
and each diagonal. Measure the clearance between
the straight-edge and combustion surface
with a feeler
gauge.
Measurement procedure
Straightedge
n
feeler gauge
Cylinder head distortion
mm
Standard Wear limit
0.05
or less
0.15
2-1.2 Checking for cracks in the combustion surface
Remove the fuel injection nozzle, intake and exhaust
valve and clean the combustion surface. Check for discol-
oration or distortion and conduct a color check test to
check for any cracks.
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Printed in Japan
HINSHI-H8009
2-5
2-1 .3 Checking the intake and exhaust valve seats
Check the surface and width of the valve seats.
If they are too wide, or if the surfaces are rough, correct to
the following standards:
Seat
angle
Seat width
Intake
Exhaust
Intake valve seal
Exhaust valve seat
(3)
2:
(I)
>
w
::::J
~
.c
><
w
Intake
120·
Exhaust
90'
Standard
Wear limit
1.07 ~1.24
1.74
1.24~1,45
1.94
€,Ly,,
120·
Standard dimension
.,,
0
~
Q,)
>
<U
>
Q,)
c.:
II'.)
:s
<f- ¢35
120·
C,
0