Inspecting And Repairing Cylinder Block, Crankshaft And Piston; Measuring Cylinder Inside Diameter; Measuring Piston Outside Diameter - Mitsubishi Heavy Industries SL Series Service Manual

4. Inspecting and repairing cylinder block, crankshaft and piston

4.1 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.
Piston and piston ring
size
Size Size mark
S.T.D STD
0.25 mm O.S
25
[0.0098 in.]
0.50 mm O.S
50
[0.0197 in.]
Cylindericity of cylinder

4.2 Measuring piston outside diameter

Using a micrometer, measure the piston outside diameter at
the skirt perpendicular to the piston pins as shown in the
illustration.
Item Nominal
78.00 mm
STD
[3.0709 in.]
Piston outside 0.25 78.25 mm
diameter OS [3.0807 in.]
0.50 78.50 mm
OS [3.0905 in.]
Weight difference per piston
Cylinder inside diameter
Standard Limit
+0.060
ø 78 mm
+0.030
+0.024
[3.0709 in.]
+0.012
Standard
+0.060
ø 78.25 mm
+0.030
+0.2 mm
+0.024
[3.0807 in.]
+0.012 [0.008 in.]
+0.060
ø 78.50 mm
+0.030
+0.024
[3.0905 in.]
+0.012
± 0.01 mm
-
[0.0004 in.] or less
Standard Limit
77.93 to
77.95 mm 77.80 mm
[3.0681 to [3.0630 in.]
3.0689 in.]
78.18 to
78.20 mm 78.05 mm
[3.0779 to [3.0728 in.]
3.0787 in.]
78.43 to
78.45 mm 78.30 mm
[3.0878 to [3.0827 in.]
3.0886 in.]
±5g
[0.18 oz.] -
or less
INSPECTION AND REPAIR OF BASIC ENGINE
Measuring
directions
A
B
Measuring
points
Measuring cylinder inside diameter
Measuring piston outside diameter
Direction at right
angles to piston pin
Measuring point
6-11