MOTO GUZZI Le Mans 850 Additions And Changes To The Workshop Manual page 6

CYLINDERS • PISTONS • PISTON RINGS
Cyllnde ... (see Drwg. fIg. 349)
IntpeCtton
Measure the cylinder bore at the top, middle and
CYLINDER '"
bottom on both transversal and longitudinal di-
rections . In case off limits of values re-bore the
cylinder considering that pistons and piston
rings are available with the following oversizes:
4/ 10 and 6/ 10.
STANDARD VALUE
4/ 10 oversize 6/10 oversize
83,000 -;- 83,018
83.400 -:- 83,418
83,600 -:- 83,618
SELECTION OF CYLINDER '"
CLASS
-A_
CLASS
.e.
83,000 -+- 83,009
83,009 -;- 63,018
Note : Class ",A .. cylinders must be matched with
class .. A,. pistons ; the same for class «6 " cy-
linders and pistons.
PI.tons (see. Drwgs. fig. 349-350)
At the time the engine is overhauled, clean the
PISTON '"
121 • P.
••
standard value
74.400
+
74.600
4/ 10 oversize
74.800
+
75.000
6/10 oversize 75.000
+
75.200
PISTON '" SELECTION
CLASS .A. CLASS
.s.
82,936 -;- 82,945
82.945
+
82,954
Note: Class " A .. piston must be matched With
class " A .. cylinders; the same for class ,, 8 .. pi-
stons and cylinders.
Fitting of
a
piston onto
a
con-rod
Before fitting a piston on to a con-rod, it is ne-
cessary to heat it in oven in oil bath at about
60 'C; this will allow a light dilatat io n of piston
holes, thus making the introduction of the piston
pin easier.
COUPLING DATA BETWEEN PISTON PIN
AND PISTON HOLES (see Drwg. fig . 350)
PISTON RINGS
Each piston fits three types of pistons rings:
17.
piston crown and the piston ring slots of all
carbon deposits. Check then the clearance bet-
ween cylinders and pistons relating to 0 selec-
tion. If such clearance is over the table values,
it will be necessary to re-bore the cylinder consi-
dering that the piston is available with the follo-
wing oversize: 4/ 10 and 6/ 10.
Pistons must be balanced; a weight difference
of 1,5 gr is allowed. The selection measure must
be taken at 22 mm from the piston bottom. (see
Drwg. fig . 349 and Selection Table) .
When fitting a piston pay attention that both the
piston selection mark and the wording ·SCA ..
(exhaust) face the cylinder exhaust hole.
121 d <l •
••
82.000
+
82.200
82.400
+
82.600
82,600 -;- 82.800
1 - Upper se.1 ring
standard
0
4/ 10 oversize
6/ 10 oversize
ring thickness
ring gap
slot clearance
" • a •
~
82,936 -;- 82,954
83,336 -;- 83,354
83.536
+
83.554
mm 83,000
mm
83,400
mm 83,600
mm 1,490
+
1,478
mm 0,30
+
0,45
mm 0,30
+
0,62
2 - Middle seal ring, step 011 scraper
standard
0
4/ 10 oversize
6/ 10
oversize
ring thickness
ring gap
slot clearance
3 - 011 scraper ring
standard
0
4/ 10 oversize
6( 10 oversize
ring thickness
ring gap
slot clearance
mm 83,000
mm
83,400
mm 83,600
mm 1,490
+
1,478
mm 0,30
+
0,45
mm 0,30
+
0,062
mm
83,000
mm
83,400
mm
83,600
mm 3,900
+
3,878
mm
0,25
+
0,40
mm
0,042
+
0,060