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INSPECTION AND REPAIR OF BASIC ENGINE
1. Inspecting and repairing cylinder head and valve mechanism
1.1 Measuring clearance between rocker
bushing and rocker shaft
Measure the rocker assembly inside diameter and the rocker
shaft diameter. If the clearance exceeds the limit, replace
either rocker assembly or rocker shaft with a new one.
Item
Nominal
Rocker bushing
ø 19 mm
inside diameter
[0.75 in.]
Rocker shaft
ø 19 mm
outside diameter
[0.75 in.]
Clearance
between rocker
-
bushing and shaft
1.2 Measuring valve stem outside diameter and
valve guide inside diameter
Measure the diameter at the top and bottom ends at right
angles to the outer and inner surfaces, since valve stems and
valve guides are more likely to wear at both ends. If the
outside diameter is less than the limit, or the clearance
exceeds the limit, replace either the valve or the valve guide
with a new one.
Item
Nominal
ø 8 mm
Valve
Inlet
[0.31 in.]
stem
outside
ø 8 mm
Exhaust
diameter
[0.31 in.]
Clearance
Inlet
-
between
valve stem
and valve
Exhaust
-
guide
Valve guide
14 mm
mounting dimension
[0.55 in.]
6-2
Standard
Limit
19.010 to 19.030 mm
[0.7484 to 0.7492 in.]
18.980 to 19.000 mm
[0.7472 to 0.7480 in.]
0.010 to 0.050 mm
0.070 mm
[0.0004 to 0.0020 in.]
[0.0028 in.]
Standard
Limit
7.940 to 7.955 mm
7.900 mm
[0.3126 to 0.3132 in.]
[0.3110 in.]
7.920 to 7.940 mm
7.850 mm
[0.3118 to 0.3126 in.]
[0.3091 in.]
0.065 to 0.095 mm
0.150 mm
[0.0026 to 0.0037 in.]
[0.0059 in.]
0.080 to 0.115 mm
0.200 mm
[0.0031 to 0.0045 in.]
[0.0079 in.]
13.9 to 14.1 mm
[0.547 to 0.555 in.]
Measuring
direction
-
-
Measuring clearance between rocker bushing and
Measuring valve stem outside diameter
Inside
micrometer
-
Measuring valve guide inside diameter
Measuring
direction
rocker shaft
Measuring
directions
Measuring
points
Measuring
directions
Measuring
points
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