1D-112 Engine Mechanical: For J20 Engine
Pistons, Piston Rings, Connecting Rods and
Cylinders Inspection and Cleaning
S5JB0A1426039
Inspection
Cylinder
• Inspect cylinder walls for scratches, roughness, or
ridges which indicate excessive wear. If cylinder bore
is very rough or deeply scratched, or ridged, rebore
cylinder and use over size piston.
• Using a cylinder gauge, measure cylinder bore in
thrust and axial directions at two positions as shown in
figure.
If any of following conditions is noted, rebore cylinder.
1) Cylinder bore diameter exceeds limit.
2) Difference of measurements at two positions
exceeds taper limit.
3) Difference between thrust and axial measurements
exceeds out-of-round limit.
Cylinder bore diameter
Standard: 84.000 – 84.020 mm (3.3070 – 3.3078
in.)
Limit: 84.050 mm (3.3090 in.)
Taper and out-of-round
Limit: 0.10 mm (0.004 in.)
NOTE
If any one of four cylinders has to be rebored,
rebore all four to the same next oversize.
This is necessary for the sake of uniformity
and balance.
Pistons
• Inspect piston for faults, cracks or other damages.
Damaged or faulty piston should be replaced.
• Piston diameter:
As indicated in figure, piston diameter should be
measured at a position 26.5 mm (1.04 in.) (“a”) from
piston skirt end in the direction perpendicular to piston
pin.
Piston diameter
• Piston clearance:
Measure cylinder bore diameter and piston diameter
to find their difference which is piston clearance.
Piston clearance should be within specification as
follows. If it is out of specification, rebore cylinder and
use oversize piston.
Piston clearance
0.02 – 0.04 mm (0.0008 – 0.0015 in.)
NOTE
Cylinder bore diameters used here are
measured in thrust direction at two positions.
• Ring groove clearance:
Before checking, piston grooves must be clean, dry
and free of carbon.
Fit new piston ring (1) into piston groove, and
measure clearance between ring and ring land by
using thickness gauge (2).
If clearance is out of specification, replace piston.
Ring groove clearance
1. 50 mm (1.96 in.)
2. 95 mm (3.74 in.)
I5JB0A142046-01
Standard
83.9700 – 83.9900 mm
(3.3059 – 3.3067 in.)
Oversize: 0.50 mm
(0.0196 in.)
84.4700 – 84.4900 mm
(3.3256 – 3.3264 in.)
Item
Standard
Limit
Top
ring
0.03 – 0.07 mm
(0.0120 – 0.0027 in.)
0.12 mm (0.0047 in.)
2nd
ring
0.02 – 0.06 mm
(0.0008 – 0.0023 in.)
0.1 mm (0.0039 in.)
Oil ring
0.06 – 0.15 mm
(0.0024 – 0.0059 in.)
—
I2RH01140157-01
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