INSPECTION AND REPAIR OF BASIC ENGINE
6-2
1. Inspecting and repairing cylinder head and valve mechanism
1.1 Measuring distortion of the bottom surface
of the cylinder head
&$87,21
Refacing of cylinder head should be kept to an abso-
lute minimum.
Excessive grinding of the cylinder head may result in
defects such as defective combustion and stamping
(contact between piston and valve).
With a straight edge placed on the bottom face of the
cylinder head, measure the bottom face distortion using a
feeler gauge. If the measurement exceeds the limit, grind the
bottom face using a surface grinder.
Measuring distortion cylinder head bottom face
1.2 Measuring clearance between rocker arm
and rocker shaft
Measure the inside diameter of the rocker arm and outside
diameter of the rocker shaft.
Replace the rocker arm or rocker shaft if the clearance
exceeds the limit.
Measuring clearance between rocker arm
and rocker shaft
1.3 Measuring perpendicularity and free length
of valve spring
Measure the perpendicularity and free length of the valve
spring. If the limit is exceeded, replace the valve spring with
a new one.
Measuring perpendicularity and free length of
valve spring
Item Standard Limit
Bottom surface distortion
0.05 mm
[0.0020 in.] or less
0.10 mm
[0.0039 in.]
Measuring points and directions
Item Nominal Standard Limit
Rocker arm
inside diameter
ø 18.9 mm
[0.744 in.]
18.910 to 18.930 mm
[0.7445 to 0.7453 in.]
-
Rocker shaft
diameter
ø 18.9 mm
[0.744 in.]
18.880 to 18.898 mm
[0.7433 to 0.7440 in.]
-
Clearance
between rocker
arm and shaft
-
0.012 to 0.050 mm
[0.0005 to 0.0020 in.]
0.200 mm
[0.0079 in.]
Measuring
directions
Measuring
directions
Measuring
points
Item Standard Limit
Free length 47 mm [1.85 in.]
46 mm
[1.81 in.]
Squareness
ǰ = 2.0°or less
Ǎ = 0.2 [0.0079]
or less
Lf = 47 mm
[1.85 in.]
Ǎ = 0.5 mm
[0.020 in.]
over entire
length
Rest length
/load
39.0 mm [1.535 in.]/
131 to 145 N
{13.3 to 14.7 kgf}
[29 to 32 lbf]
30.1 mm [1.185 in.]/
279 to 309 N
{28.5 to 31.5 kgf}
[63 to 69 lbf]
-15%
ٌ
Lf
ǰ
Free length
Spring perpendicularity (gap)
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