97
Fig. 8.12
Fig. 8.15
Fig. 8.13
L
Fig. 8.14
T
A
U
M
H
W1
W2
H
V
Tab. 8.7
Tab. 8.8
ED0053030410
INFORMATION ABOUT OVERHAULING
8.5.4 Piston dimension check
Clean the piston thoroughly.
Measure the diameter of the piston at 12 mm (quota L) from
the base of the skirt in correspondence with the graphite
lubrication windows M.
Refer to Tab. 8.8 t o e s t a b l is h t h e c l ea r a n c e v a lu e o f t h e p i s t o n s
with a decreased diameter.
In correspondence with point W, there are:
3 digits for the STD piston;
3 d i g i t s f o l l o w e d b y R f o r a p i s t o n w i t h a n i n c r e a s e d d i a m e t e r o f 0 . 2 0 m m;
+0.5 for a piston with an increased diameter of 0.50 mm
+1 for a piston with an increased diameter of 1.00 mm;
If clearance between cylinder and piston is greater than 0,074
mm, the piston and seal rings must be replaced.
Important
• Tab. 8.8 details the dimensional values of new components
only.
8.5.3 Piston rings check
Insert ring U into the cylinder, measure value H (distance
between the points of ring U).
Repeat for all the seal rings.
If the measured value H does not correspond to the values
indicated in the table (Tab. 8.7), replace the seal rings U.
Important
• Seal rings cannot be replaced separately.
NOTE: refer to Fig. 8.17 to locate the rings.
8.5.2 Checking the gudgeon pin-pin axes are parallel
Lubricate gudgeon pin A and bearing R (Fig. 8.10).
Insert the gudgeon pin into bearing R.
Use a dial gauge to check the axis parallelism of the connecting
rod big end and small end.
The parallelism deviation (value V) measured at the tip of the
gudgeon pin, must be a MIN of 0,015 and MAX of 0,030 mm.
If the parallelism values do not comply with the specied ones,
replace the connecting rod T.
PISTON
Ø
CYLINDERS
(± 0.007 mm)
Ø PISTON
(± 0.007 mm)
CLEARANCE
VALUE
(mm)
STD 96.010 95.950
0.046 - 0.074
+0.20 96.210 96.150
+0.50 96.510 96.450
+1.00 97.010 96.950
RINGS
H (mm)
U1 0.30 - 0.15
U2 0.50 - 0.70
U3 0.20 - 0.40
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