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IDLE ADJUSTING
NEEDLE
IDlE
MAIN JET
ADJUST
Fig.65
Carburetor -
63~1
and
263~I
Series
desired idling speed and repeat the
adjustment of idling jet "A".
iVi
th the boat
under way on
smooth
water,
open the throttle
approxi-
mately 75%.
Turn the high
speed
jet
"B"
in until the
engine loses
power
and RPM.
Now open
the
jet
slowlyuntil the engine runs smoothly
and
at its
higbest
RPM for
this
throttle setting.
The carburetor
should now
be cor-
rectly adjusted for
smooth opera-
tion
and
maximum
pouer
at
all
speeds.
A
slightly rich
fuel mix-
ture is
preferable to a
lean mix-
ture as a
lean mixture has the ap-
parent
effect
'of
reducing
the
octane rating
of the fuel
and can
result in a tendency toward detona-
tion
(ping),
burned
valves
and
scored or 'Worn cyl inders. Therefore,
do not
lean out the
fuel
mixture
in an attempt at fuel economy.
Knight engines
with serial
number
4979 to 6346 were
equipped
with a
fixed main jet
carburetor intended
to discourage tbe
general tendency
to lean
out the
fuel mixture
for
economy but which
is actually det-
rimental
to the
engine.
Standard
-52-
Fig.66
Carburetor -
61~
Series
jet size is No. 42
(2.1 mm.)
This
jet size should be
correct for all
applications., However, if the oper-
ator
desires very
fine tuning
he
may try
jets varying
from size 41
to 44. but not scalIer than 41.
At
the
bottom ot"
the
car'buretor
float bowl
will be found a hexagon
head
brass
plug ';7bere
a ve.'.rial>le
main jet
is usually
found on mar-
ine carburetors.
The
mein jet
is
reached by removing this plug.
The
jet itself is a soall, brass threaded
cylinder
uith
a
shoulder
e~d
a
screwdriver slot at one end.
ne~ove
and
instC'Jll the jet
't"/ith
F:,
SC1'e\1-
driver
using
care
Dot to
damage
the
jet
or
the
threeds
in
the
carburetor. !Jowl casting.
,The size
number
is
stamped
on the
end of
the jet.
This carburet
01' ,
part number
9005
120,
has a
t'rlo-hole
idle
system
that
is
rf>,ther
sensitive
in ad-
justment.
It
't1ill
require
more
care
in
adjusting
tbe
idle
jet
than with
the
former
Knight car-
buretor.
The pC'Jrt number of
each carburetor
model will be
found stawped on the
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