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tension wire
from
the spark
plug), increase
the
engine
speed
until
the speedometer
reads
50
km/h.
Wait several seconds
to make. sure
that the
condition
achieved is steady. Switch on the second cylinder
and, at the
same time, switch off
the
first
one.
By turning the uni-
ons
on
the
carburettor covers, raise
or
lower the
throttle
until
the
speedometer
indicates the same sp.eed.
Since
it takes
r
elatively
much
time
to perform
this
adjustment,
care
must
be
ta·
k en to
prevent 'the
engine
from overheating.
When
the throttle
is fully
raised,
the amount
of
fuel passing
through the atomizer
is
dependent
mainly on
the
throughput
of the
main jet.
The engine
operation
under average load
conditions
depends
on
the
position of the needle in the
throttle,
therefore,
the
adjustment
of the
carburettors wilil
consist
in the
selection
of the proper posi-
tion of the needle. Whenever
it
is necessary to enrich the mixture
(for instance, when passing from the
summer operating
period to
the
winter,
or during running-in period)
or
if
the
eng·
i ne
power has
to
be increased
at the expense
of its
operating economy,
the
carbu-
rettors
are
also
adjusted
by appropriately
changing the position of
the
needle.
The adjusting needle is linked to
the
throttle body
by
means
of
reta·
i ner 23. The needle is provided with six
annul
ar
grooves.
By
bringing the retainer into each of the
grooves,
it
is possible to ob-
tai
n
six
dif.ferent
positions of
the
car,burettor a·djustment. The
lower
the
position
of
the needle, the weaker the mixtture, the higher the po-
s·ition
of
the needle,
the richer
the mixture.
In the case
of the
average load
opera~ion,
the carburettor
is
che-
cked for
proper
adjustment
by
sh
arply inc-reasing the engine speed.
If,
as the
result of
such an increase,
bangs
are
heard
in the
carbu-
rettor,
the
mixture
must
be
enriched by lifting
the
needles
being
ad-
justed,
by one
or two
divi·
s ions.
Care of
Carburettors
It is good
praotke
to wash and
blow through
the carburettors
after every 5000 km. Before washing the carburettors, screw off
plug 6
(Fig. 13),
take out fuel filter 9 and wash it. Following that,
blo~v
through
the jet
in the channel
from
plug
14
end.
If
idling
jet
15
is clogged, screw it out and
bl·ow through.
Never
attempt
to
use
a steel wire to
clean
the
j
ets as this
may
dis'tunb
the jet
cross-.section and, consequently, will
·
i mpair
the
car-
burettor operation.
Do
not
screw out the
main jet, unless
it
is
necessary to do so, as
this may cause damage to the jet itself and to its gasket.
In case the throttle
has
to
be
dismanbled
(change
of the position
of the adjusting
needle,
removing of the thrott1e
cable)
,
detach
the
throttle
body
and its
s·
i de piece by overcoming the effort of the ex-
pansion
~pring
.
The latter
is also used as a check spring to prevent
an occasiOnal separation of the body and the side piece.
36
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