l
Honing or reboring cylinders:
1)
When any cylinder needs reboring, all other
cylinders must also be rebored at same time.
2) Select oversized piston according to amount
of cylinder wear.
I
Size
I
Piston diameter
O/S 0.25
74.220 74.230
-
mm
(2.9220
-
2.9224
in.)
74.470 74.480
-
o/s 0.50
mm
(2.9318
-
2.9322
in.)
3) Using micrometer, measure piston diameter.
1. 15 mm (0.59 in.)
Fig.
3-5-30
Measuring piston diameter
4) Calculate cylinder bore diameter to be
rebor-
ed.
D=A+B-C
D : Cylinder bore diameter to be rebored.
A : Piston diameter as measured.
8 : Piston clearance = 0.02
-
0.04 mm
(0.0008
-
0.0015 in)
C : Allowance for horning = 0.02 mm
(0.0008 in)
5) Rebore and hone cylinder to calculated dimen-
sion.
NOTE:
Before reboring, install all main bearing caps in
place and tighten to specification to avoid
distortion of bearing bores.
6) Measure piston clearance after honing.
Piston and Piston Rings
Clean carbon from piston head and ring grooves,
using a suitable tool.
Inspect piston for faults, cracks or other damage.
Damaged or faulty piston should be replaced.
0
Piston diameter:
As indicated in Fig. 3-5-31, piston diameter
should be measured at the height of 15 mm
(0.59 in) from piston skirt end in the direc-
tion perpendicular to piston pin.
Standard
73.970
-
73.990 mm
(2.9122
-
2.9129 in.)
Piston
diameter
Oversize:
0.25 mm
(0.0098 in.)
0.50 mm
(0.0196 in.)
74.220 74.230
-
mm
(2.9220
-
2.9224 in.1
74.47
-
74.48 mm
(2.9319
-
2.9322 in.)
1. 15 mm (0.59 in)
Fig. 3-5-3 1 Measuring piston diameter
with micrometer
l
Piston clearance:
To calculate piston clearance, measure cylin-
der bore diameter and piston diameter. The
piston clearance is difference between cylinder
bore diameter and piston diameter. 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 measured in thrust
direction at two positions as shown in Fig.
3-528 should be used for calculation of piston
clearance.
3-26