Motobecane 40 - Page 19

EXAM
I NAT
I ON
OF
THE
CYL
I
NDER HEAD
AND
CYL I NDER
Examinatjon
of the
Cylinder
Head:
Check
that the
cylinder
head
bottom
base
is
flat
(qrina
it
with
a
sun-
face
plate
if
necessary).
Refit
the spark
plug
and check the decompressor
valve
for
leakage by
pouring
fuel
in
the
combustion
chamber
(fjg.
1).
Except in
case
of
absolute necessity,
the decompressor valve should not
be
removed
from
the
cyl
inder head
assembly.
In
case of leakage
and
if
the
valve
is
not worn
out, tap
the
valve head
gently
to
seat.
Examination
of the
Cyl inder:
Make
sure
that
the
cylinder wall
is
neither scuffed not scored
(lack
of
chromium
plated
surface).
Measure
the
p'iston
cl earance
(d'ifference
between
the
mi nimum
cyl
i nder
bore
and
the
maximum
piston
diameter),
the
piston
rins end
gap
(fig
.
2)
and
the
clearance between
ring
and
groove.
o
Fis. 1
Fig.2
R0
15
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