Float Level Adjustment; Su Twin Carburetors Adjustment/Dismantling/Assembly; Piston And Suction Chamber Dismantling; Nozzle Dismantling - Datsun 510 series Workshop Manual

FLOAT LEVEL
Adjustment
A constant
fuel level in the float chamber is maintained
by
the float and ball valve
Fig
D 12 If the fuel level is not in
accordance with the level gauge line it will be
necessary to
care
fully bend the float
seat
until the float upper position is correctly
set
Fig D 13
The clearance H
between the valve
stem
and float
seat
should be 1 0
mm
0 039 in with the float
fully
lifted
as
shown
Adjustment
can
be carried
out by carefully bending
the float
stopper Fig D 14 until the required clearance is obtained
SU TWIN CARBURETTORS
Adjustments
It is essential that the
two
carburettors
are
correctly adjusted
if peak
m3l1ce
and economical fuel consumption is
to
be
realized Incorrect carburettor
a l j u s t m e n t
will have
an
adverse
affect
during idling and
on
acceleration
etc
Carburettor synchronization and idling adjustment
Run the
engine
until it reaches its normal
operating
temperature
remove
the air cleaner and slacken the front and
rear
throttle adjusting
screws
the balance
screw
and the fast
idling setting
screw
Make
sure
that the front and
rear
throttle
shafts
are
not
connected
Fully tighten
the
idling adjustment
nuts
of the front and
rear
carburettors
Fig
D 1 5
the back
off each nut by
an
equal
amount
and by
one
and
a
half to two
tUrns
Screw in the front and
rear
throttle adjusting
screws
by
a
few
turns
and
start
the engine Allow the engine
to
reach its
normal
operating temperature
before
proceding
to the next
stage
Adjust
the front and
rear
throttle adjusting
screws
until
the
engine speed
is reduced
to
approximately
600 700
r
p
m
The
engine
should
turn
over
smoothly
and
consistently Apply
a
flow
meter to
the front carburettor air cleaner
flange
and turn
the
adjustment screw on
the flow
meter
so
that the upper end
of the float in the glass tube is
in
line with the scale Uft off the
flow
meter and
apply
it to the
rear
carburettor air cleaner flange
without
altering
the
setting
of the flow
meter adjusting
screw
If the
position
of the flow
meter
float is
not aligned
with the
scale adjust the rear
carburettor throttle adjusting
screw
to
align the float with the mark
on
the scale
With the carburettor flow
correctly adjusted turn
the
idling adjustment
nuts
of both carburettors approximately 1 8
of
a
turn either way to
obtain
a
fast and stable engine speed
Both
nuts must be turned
by an equal
amount
Back off the front and
rear
throttle adjusting
screws
and
adjust the engine speed
to
the specified
value of 650
r
p
m for
the standard engine
or
700
r
p
m
with vehicles fitted with
automatic transmission Make
sure
that the air flow of both
carburettors remains
unchanged
Screw in the balance
screw
until the
screw
head
contacts
the throttle shafts without
changing the idling
speed
setting
Move the throttle
connecting
shaft and accelerate the
engine
a
few times then check that the
idling speed
is
unchanged
Turn the fast idle setting screw
to
increase the engine speed
to
approximately
1500
r
p
m
and recheck with the flow
meter
that the air flow for both carburettors is correctly
matched If
the air flow is
uneven
it will be necessary to
readjust
the balance
screw
Finally
back off the fast idle
setting
screw
Fig
D 16
and decrease the engine speed Apply
the flow
meter to the
carburettors
to
confirm that the float positions
are even
Re
adjust if necessary by means
of the throttle adjusting
screws
Stop
the engine and fit the air cleaner
SU TWIN CARBURETTOR
Dismantling
Piston and suction chamber Dismantling
Unscrew the
plug
and withdraw the
piston damper Fig
D
17 Remove the four
set screws
and lift out the suction
chamber withdraw the
spring nylon
washer and the
piston
Take
care
not
the damage the jet
needle and the interior of the
suction chamber
Do
not
remove
the jet needle from the piston unless
absolutely
necessary
If
a
replacement is
to
be fitted
ensure
that
the shoulder of the needle is flush with the lower face of the
piston
This
operation can
be
accomplished by holding
a
strai
edge
over
the shoulder of the needle and then
tightening
the
set
screw as
shown in
Fig
D 18
Wash the suction chamber and piston with dean solvent
and
dry
with
compressed
air Lubricate the
piston rod with
a
light
oil Do NOT lubricate the
large
end of the
piston
or
the
interior of the suction chamber
NOZZLE Dismantling
The nozzle See
Fig D 19
can
be removed quite easily
but should
not
be dismantled unless
absolutely
necessary
as
reassembly
of the nozzle sleeve washer and nozzle sleeve
set
screw
is
an
extremely intricate operation
To
remove
the nozzle detach the
connecting plate
from
the nozzle head pulling lightly
on
the starter
lever
to
ease
the
operation
Loosen the retaining clip take off the fuel line and
remove
the nozzle Be careful
not to
damage either the
jet
needle
oc
the nozzle Remove the idle adjusting
nut
and spring
The nozzle sleeve
can
be removed if
necessary
by taking
out
the
set
screw
but
as
previously
stated should
not
be dismantled
unless absolutely
necessary
SU TWIN CARBUREfTOR
Assembly
Assemble the piston assembly into position but do
not
fill with
damper
oil
Assemble the nozzle sleeve washec and
set
screw
by
temporarily tightening the
set
screw Set the
piston
to
its fully
closed
position
and insert the nozzle until it
contacts
the nozzle
sleeve When the nozzle jet
contacts
the jet needle the nozzle
sleeve
must
be
slightly adjusted so
that it is at
right angles
to
the
centre
axis and
positioned to
leave the nozzle
jet
clear of the
jet needle Raise the
piston
without disturbing the
setting
and
allow it
to
drop
The piston should drop smoothly until the
stop pin
strikes the venturi with
a
liaht
metallic click See below
under
Centering
the
jet Tighten
the nozzle sleeve
set
screw
remove
the nozzle install the idle adjustinJ spring and adjusting
nut
on
the nozzle sleeve and refit the nozzle
39