Mitsubishi Heavy Industries S3L, Service Manual

Page: 73 / 200

INSPECTION AND REPAIR OF BASIC ENGINE
6-13
4.5 Measuring piston pin bore diameter and
piston pin outside diameter
Measure the piston pin bore diameter and piston pin outside
diameter. Replace if the limit is exceeded.
Measuring piston pin bore and piston pin
4.6 Inspecting connecting rod bend and twist
(1)
Measure the dimensions of C and L in the illustration to
check bend and twist of the connecting rod. Straighten
the connecting rod with a press to meet the standard.
If the standard is exceeded after correction, replace the
connecting rod with a new one.
Inspecting connecting rod bend and twist
(2)
In general, a connecting rod aligner is used to check
bend and twist.
Note: Before checking bend, tighten the connecting rod cap
to the specified torque.
Measurement with connecting rod aligner
(3)
To inspect the connecting rod with the piston installed,
turn the piston upside down and place it on a surface
plate. Insert a round bar having the same diameter as
the crankpin into the big-end bore, and measure the
height of the bar using a dial gauge.
Measuring bend of connecting rod
Item Nominal Standard Limit
Piston pin out-
side diameter ø 23 mm
[0.91 in.]
22.944 to 23.000 mm
[0.9033 to 0.9055 in.]
-
Clearance
between piston
pin bore and
piston pin out-
side diameter
-
0.006 to 0.018 mm
[0.0002 to 0.0007 in.]
0.050 mm
[0.0020 in.]
Measuring
locations
Measuring
directions
C
C
L
L
Piston
pin
Connecting rod bend
Connecting rod twist
Unit: mm [in.]
C
100 3.94
0.05 0.0020
L
[ ]
C
100 3.94
0.05 0.0020
L
[ ]
Item Standard Limit
Bend and twist of
connecting rod
0.05/100 mm
[0.0020/3.94 in.]
or less
0.15/100 mm
[0.0059/3.94 in.]
C
A B
D