INSPECTION AND REPAIR OF BASIC ENGINE
6-20
4.14 Measuring cylinder inside diameter
Use a cylinder gauge to measure the inside diameter and
cylindericity of the cylinder at three locations in the A and B
directions as shown in the illustration.
If any one of the cylinders exceeds the repair limit, bore all
the cylinders and replace the pistons and piston rings with
oversize ones.
Measuring cylinder inside diameter
4.14.1 Reboring cylinder
&$87,21
(a) If the inside diameter of cylinder exceeds the limit,
replace the cylinder block.
(b) Bore the cylinders in the cylinder-number
sequence to prevent heat-induced distortion.
(1) Pistons are available in two sizes (0.25, 0.50 oversizes).
Select the piston size for all cylinders based on the
largest cylinder bore that has been measured.
(2) Measure the outside diameter of the piston that has
been selected.
The measuring position in the outside diameter is
shown in the illustration.
(3) Calculate the boring dimensions based on the piston
outside diameter that has been measured.
A: Piston outside diameter (mm)
(oversize piston that has been selected)
B: Clearance between piston and cylinder (standard)
0.03 mm [0.0012 in.]
C: Horning allowance 0.04 mm [0.0016 in.] or below
Boring dimension =A+B-C
(4) Bore each cylinder to dimension calculated above.
(5) Horn-finish each cylinder to achieve the final
dimension (the piston outside diameter plus the
clearance between the oversize piston and the cylinder
bore.)
Measuring piston outside diameter
Piston and
piston ring size
Cylinder inside diameter
Size
Size
mark
Standard Limit
S.T.D STD
88.000 to 88.035 mm
[3.4646 to 3.4659 in.]
Standard
+0.2 mm
[0.008 in.]
0.25 mm O.S .
[0.0098 in.]
25
88.250 to 88.285 mm
[3.4744 to 3.4758 in.]
0.50 mm O.S.
[0.0197 in.]
50
88.500 to 88.535 mm
[3.4842 to 3.4856 in.]
Cylindericity of cylinder
0.015 mm
[0.0006 in.] or less
-
A
B
Measuring
directions
Measuring
points
14 mm [0.55 in.]
Direction at
right angles
to piston pin
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