Inspect gear teeth of crankshaft. If teeth are badly worn,
chipped, or some are missing, replacement of crankshaft
will be necessary.
Inspect crankshaft bearing surfaces for scoring,
grooving, etc. Measure running clearance between
crankshaft journals and their respective bearing bores.
Use an inside micrometer or telescoping gauge to
measure inside diameter of both bearing bores in vertical
and horizontal planes. Use an outside micrometer
to measure outside diameter of crankshaft main
bearing journals. Subtract journal diameters from their
respective bore diameters to get running clearances.
Check results against tolerances in Specifications. If
running clearances are within specification, and there
is no evidence of scoring, grooving, etc., no further
reconditioning is necessary. If bearing surfaces are worn
or damaged, crankcase and/or oil pan will need to be
replaced.
Inspect crankshaft keyways. If worn or chipped,
replacement of crankshaft will be necessary.
Inspect 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
are exceeded, it will be necessary to either replace
crankshaft or regrind crankpin to 0.25 mm (0.010 in.)
undersize. If reground, a 0.25 mm (0.010 in.) undersize
connecting rod (big end) must then be used to achieve
proper running clearance. Measure crankpin for size,
taper, and out-of-round.
Connecting rod journal can be ground 1 size under.
When grinding crankshaft, grinding stone deposits
can get caught in oil passages, which could cause
severe engine damage. Removing crankpin plug when
crankshaft is ground provides easy access for removing
any grinding deposits collected in oil passages.
Use following procedure to remove and replace plug.
Procedure to Remove Crankshaft Plug
1. Drill a 3/16" hole through plug in crankshaft.
2. Thread a 3/4" or 1" long self-tapping screw with a flat
washer into drilled hole. Flat washer must be large
enough to seat against shoulder of plug bore.
3. Tighten self-tapping screw until it draws plug out of
crankshaft.
Procedure to Install New Plug:
Use 1 single cylinder camshaft pin as a driver and tap
plug into plug bore until it seats at bottom of bore. Make
sure plug is tapped in evenly to prevent leakage.
Remove Flywheel End Oil Seal
Remove oil seal from crankcase.
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 cylinder bore for scoring. In severe cases,
unburned fuel can cause scuffing and scoring of cylinder
wall. It washes necessary lubricating oils off piston and
cylinder wall. As raw fuel seeps down cylinder wall,
piston rings make metal to metal contact with wall.
Scoring of cylinder wall can also be caused by localized
hot spots resulting from blocked cooling fins or from
inadequate or contaminated lubrication.
If cylinder bore is badly scored, excessively worn,
tapered, or out-of-round, resizing is necessary. Use an
inside micrometer to determine amount of wear (refer
to Specifications), then select nearest suitable oversize
of either 0.25 mm (0.010 in.) or 0.50 mm (0.020 in.).
Resizing to 1 of these oversizes will allow usage of
available oversize piston and ring assemblies. First,
resize using a boring bar, then use following procedures
for honing cylinder.
Disassembly/Inspection and Service
52
24 690 37 Rev. B
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