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Out-of-Roundness and Conicity of
Crankshaft Journal and Pin
If the measured
value exceeds the limit, replace the
crankshaft.
Out of
roundness:
Standard value: Less than 0.01
mm
Conicity:
Standard value: Less than 0.006
mm
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To measure the bend of the
crankshaft, support it at No.1 journal and No.5 journal and
read the runout at No.3 journal.If the reading exceeds the
specified service limit, replace
the crankshaft.
| note |
The bend of the crankshaft is
a half of the dial gauge reading obtained when
the crankshaft
is rotated on turn.
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Standard value: Less than
0.2 mm
Limit: 0.05 mm
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If the runout exceeds the specified
service limit, check the flywheel assembly for loosened
bolt and defects in the joint surface to the crankshaft.
Repair or replace, if
necessary.
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If the measured value exceeds the
limit, replace the upper
crankcase.
Standard value: Less
than 0.05 mm
Limit: 0.1 mm
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| caution |
- Be sure not to use the main bearings and
26 expanded forcedly.
- When either the main bearing is
defective, replace them in
pairs.
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Measure the free span of each of
the main bearings and. If the reading for either bearing
or both exceeds the specified service limit, replace them in
pairs.
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If the reading is less than the
specified service limit, replace defective
part.
Standard
value:
No.1,2,4 and 5 bearings:
0.04 -
0.06
mm
No.3 bearing: 0.06 -
0.08
mm
Limit:
No.1,2,4 and
5 bearings: 0.1 mm
No.3 bearing: 0.1
mm
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1.If the upper crankcase
assembly includes a cylinder with any I.D. measurement
exceeding
the service limit, proceed to the following:
Rebore and
hone all cylinders to an oversize I.D. and replace the
piston and piston rings
accordingly.
A: Cylinder I.D. measuring
position (axial direction
of crankshaft)
B: Cylinder I.D. measuring position
(At right angle with crankshaft)
C: Cylinder O.D.
measuring position
2.In any upper
crankcase assembly cylinder, if the piston-to-cylinder
clearance is not
within the service limit range although the cylinder I.D.
measurements conform to the specification,
proceed to the following:
Replace the piston and piston
ring.
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1.Select an oversize piston
O.D. appropriate to the largest I.D. cylinder in the
crankcase.
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2.There are two piston
oversize dimensions available: 0.50 mm and 1.00 mm. Based on
the piston O.D.selected from them, determine a bore size to
which the cylinders are rebored
so that the specified piston-to-cylinder clearance will be
ensured.
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3.Use the following formula
when determining the cylinder reboring
dimension.
Cylinder reboring dimension =
Piston O.D. +
Piston-to-cylinder clearance
- Honing allowance
Piston-to-cylinder clearance: 0.04
-
0.05 mm.
Honing allowance.
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4.Bore all cylinders to the
dimension obtained and the hone them to the final
size.
| caution |
- Bore the cylinder in the order of No.2
→
No.4 →
No.1 →
No.3
to avoid deformation of the crank-case
due to heat generated during
boring.
- When honing cylinders, make sure that
the resulting bore dimension is equal to
the
total of piston O.D. and
piston-to-cylinder clearance. In
addition, hone them to the following
specifications:
- Honed surface roughness:
0.02 -
0.04 mm
- Crosshatch pattern angle:
15 -
25°
- Squareness of cylinder
bore: 0.05 mm
- Recheck the piston-to-cylinder clearance
after
honing.
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