Pilot Circuit; Main Circuit - Suzuki GS850G Service Manual

F U r L .5 YSTEM & CA RBUHETORS
plun_eer cliamber,
where i t
is mixed with the
starter's primary air, and then drawn
out
into
the main
bores From
the injection ports as a
well-atomized
and
concentrated fuel vcry
suitable for starting purposes. This fuel-air
mixture
is added to the fuel-air mixture being
supplied by
tlie
pilot circuit in tllc
car-
buretors.
When using the
starter,
the throtrle valve
must he completely closed. If
the throttle
valve
i s opened,
the
negative
pressure falls
and
will
not
build u p
at injection
ports and
the enyine wilt not
bc
able
ro draw sufficient
fuel. The starrer plunger has a necdle-like
tip,
which closes the starter ~ ~ n i r ' s fuel pasqa_ge.
I f
the starter knoh is not pullcd all the way up,
thc fucI passage
w i l l not open
to
let !he
gasoline flow. 1
f the starter pipe's
blccd
hole
is
clogged, the fuel
will not he atomi~ed
properly.
PI1,OT CIRCUIT
The pilot circuit consists of a pilot
air screw
0 ) ,
pilot jet
@)
,
pilot screw @!
,
and pilot
outlet ' i &
.
Rcfcr
to Fig. 9-6.
The purpose o f the pilot circuit is to supply
the
fuel
ro
the engine ur~til
il
reaches low
idling speed. The passage around the needle
jet which serves as
[he main unit's fuel in-
jection
port is wide and little gasoline can
he
drawn out through the needle jet.
T h e
passage is narrower near the pilot outlet
and
this is where
the negative pressure builds up.
This negative pressure
allows a
hiyhly
concentrated
gas
mixtiire to be drawn up
from the pilot outlet. The metered fuel arid
air arc
mixed together prior going to the pilot
fuel-air outlets.
MAIN
CIRCUIT
The main circuit consists o f
t h e
main
jet
GI,
bleed
pipe 3 ,
jet
needle
GI
,
needle
jet
@
,
throttle valve
m.
ancl air jet @ . Refer
to
Fig.
9-7. I t starts operation when the throttle
opening is about 1 /4.
Gasoline flows from the float chamber
through the main
jet,
and it
is
metered by the
air jet. The gasoline is then mixed with air
that is regulated hy the air
jet.
This mixing
occures in the bleed pipe after which the
mixhire glows into the carburetor bore
through the needle
jet.
When the throttle opening is in the
range
From
1/4
to 3/4, gasoline is metered by the
clearance between
the
needle
jet and jet
needle. When the throttle opening exceeds
3J4, the clearance between the needlc jet and
jet needle becomes larger than the main jet
hole and therefore. sasoline is metered by
the
main
jet.
The
throttle valve
has a cutaway on its intake
side to decrease the
suction
on
the needlc
j e t
by
means of vacuum nrhen the rlirotrlc
opening
is about
1/4,
and thus the flow o f
gasoline
can
be regulated.
I f the main circuit
rnalfsrnctions,
power
toss
will result in h i y l ~ speed operation. I f [lie