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ENGINE
59
NOTE
Lower and Upper bearings are not
interchangeable.
20. Install connecting rod bearing cap with
bearing shell on connecting rod. Tighten
connecting rod bearing cap mtg. nuts to
specified torque.
21. Measure connecting rod bearing bore. Record
the readings in the format given in this
manual.
22. If connecting rod big end parent bore
dimension is maintained within specified
limits, proper bearing bore dimension is
automatically achieved.
23. However, it must be physically measured and
confirmed. Measure pretension of connecting
rod bearing shell with a feeler gauge after
loosening connecting rod bearing cap
mounting nut on opposite side of bearing shell
lug.
Pretension Gap: 0.120 to 0.180 mm.
NOTE
Connecting rod bearing shells are precision
finished and should not be bored or
scraped.
Maintenance Limit
Max. permissible taper and ovality of connecting rod big end parent bore
cylindricity.
0.008 mm
0.01 mm
Max. permissible circularity and ovality of connecting rod small end parent
bore.
0.005 mm
0.008 mm
Connecting rod small end bush inside diameter (to be finished after
installation) (Piston pin oiled has thumb push fit in small end bush.)
Ø31.020 – Ø31.033 mm
Maximum permissible out of parallelism (bend) between connecting rod small
end and big end parent bores, measured at a distance of 100 mm from centre
line of connecting rod.
0.06 mm
Center to center distance between connecting rod small end and big end
parent bores
149
+0.03
mm
Maximum permissible twist of connecting rod
0.1 mm
Connecting rod big end parent bore diameter
Ø53.69+0.019 mm
Bearing shell to be selected such that clearance is maintained as
0.011 - 0.065 mm
Pre-tension of connecting rod big end bearing shells.
0.060 - 0.090 mm
Maximum permissible difference in weight of connecting rods in one engine
±3 gms
Connecting rod big end axial play
0.1 – 0.35 mm
Stage
Connecting Rod small end and big
end parent bore dia.(mm)
Crank pin journal dia with bearing
shell (mm)
Normal
50.008, 50.047
50 -0.005,-0.02
Normal 1
49.958, 49.997
49.90 -0.005, 0.02
Repair 1
49.758, 49.797
49.75 -0.005, -0.02
Repair 2
49.508, 49.547
49.5 -0.005, -0.02