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Piston clearance:
Measure cylinder bore diameter and piston diameter to find
their difference which is piston clearance. Piston clearance
should be within specification as given below. If it is out of
specification, rebore cylinder and use oversize piston.
Piston clearance
Standard : 0.032 – 0.061 mm (0.0013 – 0.0024 in.)
Limit : 0.161 mm (0.0063 in.)
Ring groove clearance:
Before checking, piston grooves must be clean, dry and free
of carbon deposits.
Fit new piston ring (1) into piston groove, and measure clear-
ance between ring and ring land by using thickness gauge
(2).
If clearance is out of limit, replace piston.
Ring groove clearance
Top ring
Standard : 0.03 – 0.07 mm (0.0012 – 0.0028 in.)
Limit : 0.12 mm (0.0047 in.)
2nd ring
Standard : 0.02 – 0.06 mm (0.0008 – 0.0024 in.)
Limit : 0.10 mm (0.0039 in.)
Oil ring
Standard : 0.03 – 0.17 mm (0.0012 – 0.0067 in.)
Piston Pin
Check piston pin, connecting rod small end bore and piston
bore for wear or damage, paying particular attention to con-
dition of small end bore bush. If pin, connecting rod small
end bore or piston bore is badly worn or damaged, replace
pin, connecting rod and/or piston. NOTE:
Cylinder bore diameters used here are measured in
thrust direction at two positions.
“a” : 19.5 mm (0.77 in.)
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Rod bearing :
Inspect bearing shells for signs of fusion, pitting, burn or flak-
ing and observe contact pattern. Bearing shells found in
defective condition must be replaced.
Two kinds of rod bearing are available; standard size bear-
ing and 0.25 mm (0.0098 in.) undersize bearing. For identifi-
cation of undersize bearing, it is painted red at the position
as indicated in figure, undersize bearing thickness is 1.605 –
1.615 mm (0.0632 – 0.0635 in.) at the center of it.
Rod bearing clearance:
1) Before checking bearing clearance, clean bearing and crank
pin.
2) Install bearing in connecting rod and bearing cap.
3) Place a piece of gauging plastic (1) to full width of crank pin
as contacted by bearing (parallel to crankshaft), avoiding oil
hole.
4) Install rod bearing cap (1) to connecting rod.
When installing cap, be sure to point arrow mark (2) on cap
to crankshaft pulley side, as shown in figure. After applying
engine oil to rod bolts and tighten cap nuts (3) gradually as
follows.
a) Tighten all cap nuts to 15 N·m (1.5 kg-m, 11.0 lb-ft).
b) Retighten them to 45°.
c) Repeat step b).
Tightening torque
Connecting rod bearing cap nuts
(a) : 15 N·m (1.5 kg-m, 11.0 lb-ft) and extra tightening 45°
twice
5) Remove cap and using a scale (1) on gauging plastic (2)
envelope, measure gauging plastic width at the widest point
(clearance).
If clearance exceeds its limit, use a new standard size bear-
ing and remeasure clearance.
Connecting rod bearing clearance
Standard : 0.029 – 0.047 mm (0.0011 – 0.0019 in.)
Limit : 0.065 mm (0.0026 in.)
1. Red paint
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6) If clearance can not be brought to within its limit even by
using a new standard size bearing, regrind crankpin to
undersize and use 0.25 mm undersize bearing.
ASSEMBLY
1) Install piston pin to piston (1) and connecting rod (2):
a) After applying engine oil to piston pin and piston pin holes
in piston and connecting rod.
b) Fit connecting rod as shown in figure.
c) Insert piston pin to piston and connecting rod.
d) Install piston pin circlips (3).
2) Install piston rings to piston :
a) As indicated in figure, 1st and 2nd rings have “T” mark
respectively. When installing these piston rings to piston,
direct marked side of each ring toward top of piston.
b) 1st ring (1) differs from 2nd ring (2) in thickness, shape and
color of surface contacting cylinder wall.
Distinguish 1st ring from 2nd ring by referring to figure.
c) When installing oil ring (3) install spacer first and then two
rails.
3) After installing three rings (1st, 2nd and oil rings), distribute
their end gaps as shown in figure. NOTE:
After checking the rod bearing clearance, make sure to
check connecting rod bolt diameter.
Refer to “Inspection” of “Connecting Rod”.
NOTE:
Circlip should be installed with its cut part facing as
shown in figure. Install so that circlip end gap comes
within such range as indicated by arrow.
1. Arrow mark
2. 1st ring end gap
3. 2nd ring end gap and oil ring spacer gap
4. Oil ring upper rail gap
5. Oil ring lower rail gap