ENGINE – Crankshaft and Flywheel
11-72
(5) Using cylinder gauge, measure the cylinder bore and
cylindricity. If worn badly, correct cylinder to an oversize
and replace piston and piston rings. Measure at the points
shown in illustration.
Standard value:
Cylinder I.D. 85.00 – 85.03 mm
Cylindricity 0.01 mm or less
BORING CYLINDER
(1) Oversize pistons to be used should be determined on
the basis of the largest bore cylinder.
Piston size identification
Size Identification mark
0.50 O.S. 50
1.00 O.S. 100
NOTE
Size mark is stamped on the piston top.
(2) Measure outside diameter of piston to be used. Measure
it in thrust direction as shown.
(3) Based on the measured piston O.D. calculate boring finish
dimension.
Boring finish dimension = Piston O.D. + (clearance
between piston O.D. and cylinder) – 0.02 mm
(honing margin)
(4) Bore all cylinders to the calculated boring finish dimension.
Caution
To prevent distortion that may result from temperature
rise during honing, bore cylinders, working from No.
2, No. 4, No. 1 to No. 3.
(5) Hone to final finish dimension (piston O.D. + clearance
between piston O.D. and cylinder).
(6) Check clearance between piston and cylinder.
Clearance between piston and cylinder:
0.02 – 0.04 mm
NOTE
When boring cylinders, finish all of four cylinders to same
oversize. Do not bore only one cylinder to an oversize.
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