6-25
Chapter 6 INSPECTION AND REPAIR OF BASIC ENGINE
5. Crankcase and Crankshaft - Inspect and Repair
5.1 Crankcase Top Surface Distortion - Measure
Apply a straight edge to the top surface of the crankcase and
measure its distortion with thickness gauges. If the value
exceeds the limit, replace the cylinder head with a new one,
or repair by grinding.
After grinding, record the maximum depth of grinding. Note
that the total grinding amount, which includes the grinding
depth of bottom surface of cylinder head, must be 0.50 mm
[0.020 in.] or less.
Crankcase Top Surface Distortion - Measure
Height From Crank Journal Center to
Crankcase Top Surface
5.2 Inside Diameter of Main Bearing Housing Bore - Measure
(1) Assemble the main bearing cap in crankcase in accor-
dance with the specified method.
Note: For tightening procedure of main bearing cap, refer to
"Main Bearing Cap - Install" of "ASSEMBLY OF BA-
SIC ENGINE."
(2) Measure the housing diameter in vertical and two diag-
onal directions.
Inside Diameter of Main Bearing Housing Bore -
Measure
5.3 Cylinder Liner Fitting Bore in Crankcase - Inspect
(1) Inspect the counterbore in crankcase. Check for cracks
in edges, uneven contact between counterbore and bot-
tom face of cylinder liner flange. If any defect is found,
reface the counterbore in crankcase.
(2) Inspect the cylinder liner fitting section in crankcase.
Check for the defects such as fretting and corrosion.
Cylinder Liner Fitting Bore in Crankcase - Inspect
Refacing depth of crankcase is to be minimum.
Excessive grinding of the crankcase may result in
defects such as defective combustion and stamping
between piston and valve.
Item Standard value Limit value
Crankcase top surface
distortion
0.1 mm [0.004] or less
0.2 mm
[0.008 in.]
Height from the crank
journal center to
Crankcase top surface
(reference value)
549.45 to 549.55 mm
[21.6318 to 21.6358 in.]
-
Straight edge
Thickness gauge
Crankcase top face roughness
549.45 to 549.55 mm
[21.631 to 21.635 in.]
ٖٖٖ
Item
Nominal
value
Standard value Limit value
Inside diameter
of main bearing
bore
ø147 mm
[5.79 in.]
147.000 to 147.025
[5.7874 to 5.7884 in.]
147.035
[5.7888 in.]
490 ± 24.5 N·m
{50 ± 2.5 kgf·m}
[361 ± 18.1lbf·ft]
[Wet]
Crankcase counterbore
Fitting bore of
cylinder liner in crankcase
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