10.3
Section 10
Internal Components
10
Crankshaft
Inspection and Service
Inspect the gear teeth of the crankshaft. If the teeth are
badly worn, chipped, or some are missing,
replacement of the crankshaft will be necessary.
Inspect the crankshaft bearing surfaces for scoring,
grooving, etc. Do not replace the main bearings unless
they shown signs of damage or are out of running
clearance specifications. If the crankshaft turns easily
and noiselessly, and there is no evidence of scoring,
grooving, etc., on the races or bearing surfaces, the
bearings can be reused.
Inspect the crankshaft keyways. If worn or chipped,
replacement of the crankshaft will be necessary.
Inspect the crankpin for score marks or metallic
pickup. Slight score marks can be cleaned with crocus
cloth soaked in oil. If wear limits, as stated in
Specifications and Tolerances are exceeded, it will be
necessary to replace the crankshaft.
Crankcase
Inspection and Service
Check all gasket surfaces to make sure they are free of
gasket fragments. Gasket surfaces must also be free of
deep scratches or nicks.
Check the cylinder bore for wear, scoring, or vertical
scratches. In severe cases, unburned fuel can cause
scuffing and scoring of the cylinder wall, it washes the
necessary lubricating oils off the piston and cylinder
wall. As raw fuel seeps down the cylinder wall, the
piston rings make metal to metal contact with the
wall. Scoring of the cylinder wall can also be caused
by localized hot spots resulting from blocked cooling
fins or from inadequate or contaminated lubrication.
Measure the cylinder bore using an inside micrometer
or bore gauge. See Figure 10-6. Compare readings
with specifications in Section 1.
Figure 10-4. Cam Lobe Checking ‘‘B’’.
Cam Lobe Dimension–B
Intake Exhaust
CS4, CS6 22.0 ± 0.05 mm 22.0 ± 0.05 mm
(0.87 ± 0.002 in.) (0.87 ± 0.002 in.)
CS8.5, CS10, 26.08 ± 0.05 mm 26.08 ± 0.05 mm
CS12 (1.03 ± 0.002 in.) (1.03 ± 0.002 in.)
Measure the camshaft journals, which fit in the ball
bearings, for wear using a micrometer. Compare with
specifications listed.
Figure 10-5. Camshaft Journal Checking.
Camshaft Journal Specifications
B
CS4, CS6 14.95 mm (0.589 in.)
CS8.5, CS10, 15.965-15.990 mm
CS12 (0.6285-0.6295 in.)
Limit 15.95 mm (0.6280 in.)
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