DATSUN 510 1969 Service Owner's Guide

inter
i
D
j

@
2l

Fig
C
3
Checking
the

ignition
timing

J
EARTH

LEAD

WIRE

SET

SCREW

OAmER

Fig
C
5
View
of
the
distributor
without

cap

Fig
C
7

Removing
the

retaining
pin

30
J

Fig
C
4

Adjusting
the
contact

points
gap

L

Fig
C
6

Removing
the
earn

2

1

1

I
7

V

J

J
1

Governor
weight

2
Oearance
for
start
and

nd

of
advanc

angle

1

Hook

4
GOllernor

spring
B

5
Com

plate

6

F7YWt
ight
pin

7
Hook

8

Goverrwrspring
A

9
Rotor

positioning
tip
@

Fig
C
8

Centrifugal
advance
mechanism

CENTRIFUGAL
ADVANCE
MECHANISM

Special
equipment
is

required
to
check
the
advance

characteristics
It
is

possible
however
to

carry
out
an
exam

ination
of

the
caffi

assembly
and
the

weights
and

springs
to

ensure
that
the
earn
is
not

seizing

Lift
off
the
distributor

cap
and
turn
the
rotor
anti
clock

wise
When

the
rotor

is
released
is
should
return
to

the
fully

retarded

position
without

sticking
If
it

does
not
return
to
the

fully
retarded

position
it
will
be

necessary
to
check
for

dirt

and
weak

springs

It
should
be
noted
that

any
wear
in
the

mechanism
or

lose
of

spring
tension
will

upset
the
advance
characteristics
and

cause

unsatisfactory
engine
running
performance
over
the

speed

range

VACUUM
ADVANCE
MECHANISM

The

diaphragm
of
the
vacuum
advance

mechanism
is

mechanically
connected
to
the
contact
breaker

plate
The
rise

and
fall
of
inlet
manifold

depression
causes

the

diaphragm
to

move

the
contact
breaker

plate
to

advance
or

retard
the

ignition

If
the
vacuum

control
unit
fails
to

function

correctly
a

check
can
be
carried
out
to
ensure
that
the
contact
breaker

plate

is

moving
freely
and
that
the

three
steel

balls
at

the

top
and

oottom
of
the

plate
are

adequately
lubricated

Also
make
sure
that
the
vacuum
inlet

pipe
is
not
blocked

or

leaking
and
is

securely
tightened

Leakage
may
be
due
to
a

defective

diaphragm
which

should

be
renewed

along
with

any
other

faulty
part
of
the
mechanism

IGNITION
DlSTRffiUTOR
Removal

and

Dismantling

Disconnect
the

battery
leads

2
Disconnect
the

high
tension
lead
at

the
coil

3
Withdraw

the
high
tension
leads
from
the
distributor

cap

4
Detach
the
suction

pipe
from
the
vacuum
control
unit

5
Mark
the

position
of
the
distributor
and
rotor
remove
the

flange
mounting
bolts

and
withdraw
the
distributor

To
dismantle
the
distributor

proceed
as

follows

Take
off
the
distributor

cap
and
remove

the
rotor

Slacken

the
two
set
screws

holding
the
contact
breaker

upper
plate

Remove
the

primary
cable
terminals
and
withdraw
the
contact

set
from

the
distributor
Fig
C
S
Remove
the
vacuum
control

unit

c
Remove
the
two
screws
and
lift
out
the
contact

breaker

plate
detach
the

clamp
the
terminal
and
the
lead

To
remove
the
cam
take
out
the
centre
screw
as

shown
in

Fig
e
6
Drive
out

the
drive

pinion
retaining
pin
with
a
drift

and
hammer
Fig
e
and
remove
the

pinion
and
washer
Take

care
not
to
stretch
or
deform
the

governor
springs
when

detaching

them
from
the

weights

IGNITION
DISTRIBUTOR

Assembling
and

Installing

Assembly
is
a
reversal
of
the

dismantling
procedure

Lubricate
the

moving
contact

pivot
and
smear
the
lobes
of
the

cam
with
multi

purpose
grease

If

the
centrifugal
advance
mechanism
has
been
dismantled

the

governor
springs
and
cams
must
be
refitted
as

shown
in

Fig
e
8
The

governor
weight

pin
6
should
be
fitted
into

the

longer
of
the
two
slots

leaving
a
certain
amount
of

clearance

for
the
start

and
end
of
the

centrifugal
advance
movement

When

installing
the
distributor
take
care
to

align
the

body

and
rotor

with
the
marks
made
during
removal
The
rotor
must

be

positioned
in
its

original
location
it
will
turn

slightly
when

the
distributor
is
inserted
and
the

gear
teeth
mesh
Remove
and

replace
the
distributor
if

the
rotor
does
not

point
to
the

align

ment

mark
until
both
distributor

body
and
rotor
are
correctly

aligned

SPARKING
PLUGS

The

sparking
plugs
should
be

inspected
and
cleaned
at

regular
intervals
not

exceeding

every
10
000
km
6000
miles

New

sparking
plugs
should
be
fitted
at

approximately
20
000

km
12
000
miles

Remove
the

plugs
and
check
the
amount
of
electrode

wear
and

type
of

deposits
Brown
to

greyish
tan

deposits
with

slight
electrode
wear

indicate
that
the

plugs
are

satisfactory
and

working
in

the
correct
heat

range

Dry
fluffy
carbon

deposits
are
caused

by
too

rich
a
mixture

dirty
air
cleaner
excessive
idling
or

faulty
ignition
In
this

case

it
is
advisable
to

replace
the

plugs
with

plugs
having
a

higher
heat

range
Oily
wet
black

deposits
are
an

indication

of

oil
in

the
combustion
chambers

through
worn

pistons
and

rings
or
excessive
clearance
between
valve

guides
and
stems

The

engine
should
be
overhauled
and
hotter

plugs
installed
A

white
or

light
grey
centre

electrode
and
bluish
burned
side

electrode
indicates

engine
overheating
incorrect

ignition
timing

loose

plugs
low
fuel

pump
pressure
or
incorrect

grade
of
fuel

Colder

sparking
plugs
should
be
fitted

The

plugs
should
be
cleaned
on
a

blasting
machine
and

tested
Dress
the
electrodes
with
a
small
file
so
that
the
surfaces

of
both
electrodes
are
flat
and

parallel
Adjust
the
spark
plug

gap
to
0
8
0
9
mm
0
031
0
035
in

by
bending
the
earth

electrode
Refit
the

plugs
and

tighten
them
to
a

torque
reading

of
1
5
2
5

kgm
II
15Ib
ft

31

TechnIcal
Data

IGNITION
DISTRIBUTOR

Type

L16
ll8
with

single
carbl

L16
L18
with
twin
arb

L14

Firing
order

Rotation

Ignition
timing
BTDC

0411
58K

0409
54K

0411
63

Dwen

angle
Hitachi
D411
58K

Hitachi
D409
54
K

Hitachi
0411
63

I
3
4

2

anticlockwise

100
at
600
r

p
m

140
at
650
c

p
m

80
at
600
r

p
m

49
550

Contact

point

gap
setting

Contact

spring
tension
0
45
0
55
mm
O
OI77
0
0217
in

0
50
0
65

kg
l
l
0
I
43
lb

Condenser

capacity
0
22
0
44
F

IGNITION
COil

Type

Spark
plugs

With

single
carb

With
twin
carb

Plug

gap

Tightening
torque
Hitachi
6
R
200

NGK
BP
5ES

NGK
BP
6ES

0
8
0
9
mm
0
031
0
035
in

1
5
2
5

kgm
II
15Ib
ft

1300cc

engine
IGNITION
TIMING

Adjustment

100
B
T
D
C
600
r

p
m

32

Fuel

System

DESCRIPTION

FUEL
TANK

FUEL
PUMP

CARBURETTOR
IDLING
ADJUSTMENT

FAST
IDLE
OPENING
ADJUSTMENT

THROTTLE
VALVES
INTERLOCK
OPENING

DASHPOT

DESCRIPTION

The

diaphragm
type
fuel

pump
shown
in

Fig
D
1
feeds

fuel

from
the
tank
to
the
carburettor
in
a

regulated
supply

according
to
the
needs
of
the

engine
A
cartridge
type
fuel

strainer

prevents
any
dirt
from

reaching
the

pump
inlet
valve

The

carburettor
fitted
to

the

engine
is
either
a
down

draught
two
barrel

type
equipped
with
a
throttle

operated

acceleration

pump
and
power
valve
mechanism

See
Fig
D
2

or
a
twin
SU
carburettor
of
the

type
shown
in

Fig
D
3
In
the

two
barrel

type
carburettor

fuel
flows
from
the

passage
at
the

bottom
of
the
float
chamber

passes
through
the

primary
main

jet
and
mixes
with
air

introduced

through
the
main
air
bleed

screw

The

petrol
and
air
mixture
is

injected
into
the
venturi

through
the
main
nozzle

Each
time
the
accelerator

pedal
is

depressed
the
throttle

opens
and
the
accelerator

pump
forces
a

jet
of

petrol
into
the

air
stream
to
allow
the

engine
to
accelerate

smoothly
See

Fig

0
4
The

power
valve
mechanism
is

operated
automatically

according
to
the
demands
made

by
the

engine
Under
light
load

i
e

part
throttle
conditions
the
intake
manifold

depression
is

transmitted
below
the
throttle
valve
the
vacuum

pulls
a

piston

upwards
against
a

spring
and
leaves
the

power
valve
closed

allowing
additional
air
to
be

admitted
through
the
air
bleed
screw

and
thereby
weaken
the

petrol
and
air
mixture
When
the
vacuum

below
the
throttle
vaJve
is
lowered

during
full
load
conditions

the

piston
is

pushed
down
opening
the

power
valve
and
providing

additional
fuel
to
enrichen
the
mixture

The
model

HJ
L
38W6
SU
twin
carburettor
is
of

the

horizontal
variable
venturi

type
and
is
used

only
on
the
1600

and
1800
cc

engines
In
this

type
of
carburettor
a

constant

flow
of
intake
air
is

maintained

by
the

automatically
adjusted

venturi

opening
this
is
accomplished

by
the
suction

piston

sliding
in
accordance
with

changes
in
the
volume
of
intake
air

Referring
to

Fig
D
5
the
suction
chamber
is
mounted
above

the
venturi
The
suction

piston
slides
vertically
within
the

chamber

and

changes
the
venturi

opening
area
The

piston
is

operated
by
a

difference
between
the

upper
vacuum

pressure

which
is

applied
through
the
suction

poct
and
the
atmospheric

pressure
which

is
introduced

through
the
air
hole
from
the
air

cleaner

The
amount

by
which
the
throttle
is

opened
causes
the

suction

piston
to
rise
or
fall
under
the
intluence
of
the

engine

suction
The

pozzle

opening
therefore

changes
and

provides
an

optimum
air
fuel
mixture
at
all

engine
speeds

The

cartridge
type
fuel
strainer
utilizes
a
fibre
strainer

element
which
should
be

replaced
every
20
000
km
12
000

miles
Removal
of
the
fuel
strainer
is
a

simple
operation
but
as

it
cannot
be
drained
the
strainer
should
not
be
removed
when
CARBURETIOR
Removal
and
Overhaul

FLOAT
LEVEL
Adjustment

SU
TWIN
CARBURmORS

Adjustments

SU
TWIN
CARBURmORS

Dismantling

SU
TWIN
CARBURETTORS

Inspection

STARTING
INTERLOCK
VALVE
OPENING

HYDRAULIC
DAMPER

the
tank
is

full
unless

absolutely
necessary

A

viscous

paper
type
air
cleaner
element
is
fitted
which

does
not

require
cleaning
and
should
be

repl
ced

every
40
000
km

24
000
miles
The
air

cleaner
fitted
on
the

single
carburettor

is
equipped
with
an

idling
compensator
to

prevent
the
mixture

from

becoming
too

rich
at

high
idling

temperatures
Additional

fresh
air
is
introduced
into
the
inlet
manifold

by
the
action
of

a
bimettalic

strip
located
in
the
air
cleaner
When
the

temperature

under
the
bonnet
is

high
the
bimetal
is

heated

by
the
hot
inlet

air
and
lifts
to
allow
the
valve
to

open
The

idling
compensator

valve

partially
opens
at

550
I310F
and
is

fully
open
at

650C

l490F
The
unit
cannot
be
dismantled
as

it
is

pre
sealed
and

correctly
adjusted
for
valve

timing
Fig
D
6
shows
the

layout

of

the
idling
compensator
piping

FUEL
TANK

Replacing

The
fuel
tank
can
be
removed
in
the
following
manner

Remove
the
rear
seat

and
back
rest

2
Take
out
the
board
behind
the
back
rest

3
Take
out
the

luggage
compartment
lining
board
and

disconnect
the
cable
to
the

petrol
gauge
unit

4
Disconnect
the
petrol
filler
tube
from
the
tank

5
Remove
the
tank
retaining
bolts
and
disconnect
the

rubber
fuel
outlet
and
return
hoses

Installation
is

a
reversal
of
the
removal

procedure
always

ensure
that
the
fuel
lines
arc
carefully
checked
for

signs
of

damage
before

replacing
the
tank

FUEL
PUMP

Testing

Pressure
and
capacity
tests
can
be
carried
out
with
the

pump
installed
in
the

following
manner

Static

pressure
test

Disconnect
the
fuel
line
at

the
carburettor
install
an

adaptor
tee

fitting
and
suitable

pressure
gauge
to
the
fuel
line

between
carburettor
and
fuel

pump
Start
the
engine
and
run
it

at

varying
speeds

The

reading
on

the
gauge
should
be
0
18
0
24

kg
sq

cm
2
6
34
Ib

sq
in
If
the

pressure
is
below
the

specified

figure
then
either
one

part
of
the

pump
has
worn

excessively

or

general
wear
has
occured
to

all
the

working
parts
The
faults

may
include
a

ruptured
diaphragm
worn
and

warped
valves

33

inter
1
j

Q

I
JJtE

1
Float
valve

2
Float

3
C1roke
aU
l

4
SmaU
venturi

primary

5

PritniJry
main
nozzle

6

Primary
main
ai
blud

7

Primmy
slow
air
bleed

8
Slow

running
jet

9
Slow
economizer

jet

10

condory
slow
ai
bleed

11

Primlry
emulsion
tube

12

Primary
main

jet

13

Idling
nozzle

14

By
pass
hole

15

Primary
throttle

vah
l

16

Secondary
smo
lllenturi

1
Z

Secondary
main
nozzle

18

Secondary
1ni1

n
air
bleed

19
Slow

running
jet

20
Slow

running
air
bhYd

34
1

G
o

1

u

40

j

t

1

fE
SV

11

t
9

Fig
D
l
The

fuel

pump

I

Cop

2

Gasket

3

Packing

4
Valve

ouembly

5
YaM

tain

6

Diaphragm

assembly

7

DiaphTagm
spring

8
Prdl
rod
9
Seal

washer

10
Seal

11

nletconnector

12
Outln

connector

J
J
Rocker

arm

sprint

J
4

Rocker
ann

15
Rocker
ann

pin

J

6

Packing

7

Spacer

If

C1l

T

l

I

I
@

51

lID

ID

I

9J

lJi

22
ill

21

23
3
f

II
I

21

Secondary
emulsio
tube

22

Secondary
main

jet

23
Bv

pass
hole

24

Secondary
thro
e

valve

25
Air

Tf

pi
I
or

LIt

Fig
D
l
Section

through
the
twin
choke

carburettor
For

LIb
ml

and
seats
or
a
weak

diaphragm
return

spring

A

pressure
above
the

specified
figure
may
be
due
to

an

excessively
strong
and
tight
diaphragm

Capacity
test

The

capacity
test
can
be

carried
out
when
the
static

pressure
has
been
tested
and
conforms
with
the

specified
figure

of
0
18

kg
sq
cm
2
6Ib

sq
inJ

Disconnect
the
fuel
line
at

the
carburettor

and

place
a

container
under
the
end
of
the

pipe
to
act
as
a
fuel

sump

Start
the

engine
and
run
it
at
a

speed
of
1000

Lp
m
The

amount

of
fuel
delivered
from
the

pump
in
one
minutc
should

be

1000
cc
2
1
US

pt

If

petrol
does
not
flow
from
the

opcned
end
of

the
pipe

at
the
correct
rate
then
either
the
fuel

pipe
is

clogged
or

the

pump
is
not

operating
correctly

If
the
latter
cause
is

suspected
the

pump
must
be
removed

and

inspected
as
described
below

FUEL
PUMP

Removing
and

Dismantling

Before

removing
the
pump
take
off
the

petrol
tank

cap

and
disconnect
the

pump
inlet
and
outlet

pipes
Blow

through

the

pipes
with

compressed
air
to

make
sure

that

they
are
not

clogged

Remove
the

pump
retaining
nuts

withdraw
the

pump
and

dismantle
it
in
the

following
order

Referring
to

Fig
D
l

Take
out
the
screws

holding
the
two

body
halves

together

and

scparate
the

upper
body
from

the
lower

body

2
Remove
the

cap
and

cap
gasket

3
Unscrew
the
eI
bow
and
connector

4
Take
off

the
valve
retainer
and
remove
the
two
valves

5
To
remove
the

diaphragm
diaphragm
spring
and
lower

body
sealing
washer

press
the

diaphragm
down

against

the
force
of
the

spring
and
tilt
the

diaphragm
at
the
same

time
so
that
the

pull
rod
can
be
unhooked
from
the
rocker

arm

link

Fig
D
7

The
rocker
arm

pin
can

be
driven
out
with
a
suitable

drift

FUEL
PUMP

Inspection
and

Assembly

Check
the

uppcr
and

lower

body
halves
for
cracks

Inspect

the
valve
and
valve

spring
assembly
for

signs
of
wear
and
make

sure
that
the

diaphragm
is
not

holed
or

cracked
also
make
sure

that
the
rocker
arm
is
not
worn
at
the

point
of
contact
with

the

camshaft

The
rocker
arm

pin
may
cause

oil

leakage
if
worn

and

should
be
renewed
Assembly
is
a
reversal
of
the
dismantling
procedure

noting
the

following
points

Fit
new

gaskets
and
lubricate
the
rocker
arm
link
and
the

rocker
arm

pin
before

installing

The

pump
can
be
tested

by
holding
it
approximately
I

metre
3

feet
above

the
level
of
fuel

and
with
a

pipe
connected

between
the
pump
and
fuel
strainer

Operate
the
rocker
ann

by
hand
the

pump
is

operating

correctly
if
fuel
is
drawn

up
soon
after

the
rocker
ann
is

released

CARBURETTOR
IDLING
ADJUSTMENT

The

idling
speed
cannot
be

adjusted
satisfactorily
if
the

ignition
timing
is
incorrect

if
the
spark
plugs
are

dirty
or
if

the
valve
clearances
are
not

correctly
adjusted

Before

adjusting
the

idling
speed
set
the
hot
valve

clearances

t
o
0
25
mm
0
0098
in
for
the
intake
valves

and

0
30
mm
0
0118
in
for
the
exhaust
valves
as
described
in

the
ENGINE

section

Idling
adjustment
is
carried
out

with
the
throttle

stop

screw
in

conjunction
with
the

idling
adjustment
screw

See

Fig
D
8

Run
the

engine
until
it
attains
its
normal

operating

temperature
and
then
switch
off

Starting
from
the
fully
closed

position
unscrew
the

idling
adjustment
screw

by
approximately
three
turns

Screw
the
throttle

stop
screw
in

by
two
or
tftr
e
turns
and

start

th
engine

Unscrew
the
throttle

stop
screw
until
the

engine
commences

to
run

unevenly
then
screw
in
the

idling
adjustment
screw
so

that
the
engine
runs

smoothly
at
the

highest
speed

Readjust
the
throttle

stop
screw
to

drop
the

engine
speed

of

approximately
600
r

p
m
is
obtained

WARNING
Do
not

attempt
to
screw

the

idling
adjustment

screw

down
completely
or
the

tip
of
the
screw

may
be

damaged

FAST
IDLE
OPENING
ADJUSTMENT

The
choke
valve
is

synchronized
with
the
throttle
valve

and
connected
to
it

by
levers
as
shown
in

Fig
D
9
The
fast

idle
opening
can
be
check

by
fully
closing
the
choke
valve
and

measuring
the
clearance
between
the

primary
throttle
valve
and

the
wall
of

the
throttle
chamber
This
clearance

being
shown

as
A

in
the
illustration
The
clearance
for

the
carburettor

types
is
as
follows

Carburettor

type
Throttle

opening

angle

180

180

190
Dimension
A

213304
361

13304
4
I

13282
331
1
55mm
0
06lin

1
55mm
0
06Iin

1
3
mm
0
051
in

35

inter
ill
j

@
pl

T
i

5

12

Fig
D
3

View
of
the
SU
twin

type
carburettors

1

Throttle
r

2
JaJana

crew

Front
throttle

adjusting
screw

4

AuxiliDry
shoft

5
Ftnt
idle

selling
lCn
W

6

Throttle

shaft

7
Rear
throttle

adjusrint
screw

8

Idling
adjustment
nuts

m

11

j
G

36
B

l
D

i
I

lli

9
3
J6

6

Fig
D
4

Accelerator

pump
mechanism

J

Pump
injuror

2

Weight

2
Outklvolve

4
Piston

5

Damper
spring

6
Piston

return

spring

7

Clip

8
Strainu

9
Inlet
lmlJe

I

Fig
D
6

Idling
compensator
1

lit

21
Fig
D
5
Section

through
the
SU
twin
carbureUor

J
Suction

chamber

Suctiull

spring

3
Hoat

chamber
corer

4
Guide

5

Nipple

6
Throttle
chamber

7
Piston
rod

8

Needle
valve

9
T7trollle
l
ob
e

J
O
Float
chtzmber

J
1
Float
Iel
cr
J
2
Float

13
Sleel
e

4

aip

5
Fuel
hose

6
Oil

cap
nut

1
7

Plunger
rod

18
Transvtne
hole

J
9
Oil

domJX

20
Suction

piston

21
Nozzle

Idling
adjustment
nut

Carburettor

type
Throttle

opening

angle

190

200
Dimension
A

213282

341

213282
221
l
3mm
0
051
in

I
4mm
0
056in

If

adjustment
is

required
the
choke
connecting
rod
can
be

carefully
bent
until
the

required
clearance
is

obtained

THROTTLE
VALVES
INTERLOCK
OPENING
ADJUSfMENT

Open
the

primary
throttle
valve
500
from
the

fully
closed

position
as
shown
in

Fig
D
I
O
At

this

angle
the
connecting

link
2
should
be
at

the
extreme

right
of
the

groove
in

the

primary
throttle
arm
The

linkage
between
the

primary
and

the

secondary
throttles
is

operating
correctly
if
the
clearance

C
between
the

primary
throttle
valve
and
the
wall
of
the

chamber
is
as
follows

Carburettor

type

213304

361

213304
421

213282
331

213282
341
Dimension
C

6
3
mm
0
248
in

6
3
mm
0
248

in

74
mm
0
291
in

74
mm
0
291
in

Adjustment
can
be
made
if

necessary
by
bending
the

connecting
link
until
the

required
clearance
is
obtained

DASHPOT
ADJUSfMENT

This

adjustment
is

only
required
on

carburettors
fitted
to

vehicles
with
automatic
transmission
Correct
contact
must
be

made
between
the
throttle
lever
and
the

dashpot
stem
See

Fig
D
II

Adjustment
can

be
carried
out
if

necessary
by

slackening
the
locknut
2
and
then

rotating
the

dashpot
in

either
direction
so
that
the
throttle
ann
touches
the
stem
at
a

throttle
valve

opening
angle
of
110
At

this
angle
the
clearance

B
between
the
throttle
valve
and
the
wall
of
the
chamber

should
be
as
follows

Carburettor

type

213304
421

213282
341
Dimension
B

0
780mm
90
0307
in

0
586mm
0
0231
in

Retighten
the
locknut
after

completing
the

adjustment

CARBURETTOR
Removal
and
Overhaul

The
carburettor
can
be
removed
from
the

engine
in
the

following
manner

Remove
the
air
cleaner

assembly

2
Disconnect
the
fuel
and
vacuum

pipes
and
the
choke
wire

from
the
carburettor

3
Remove
the
throttle
lever
and
take
off
the
nuts
and

washers

securing
the
carburettor
to

the
manifold

4
Lift
the
carburettor

away
from
the
manifold
and
discard

the

gasket

To
dismantle
the
carburettor
for
a

complete
overhaul

remove
the

primary
and

secondary
main

jets
and
needle
valves
these
are
accessible
from
the
exterior
of
the
carburettor

Remove
the
choke

connecting
rod

pump
lever
return

spring
and
set
screws
and
take
off
the
choke
chamber

The

primary
and

secondary
emulsion
tubes
can
be
with

drawn
after

removing
the
main
air
bleed
screws

If
the
accelerator

pump
is
to
be
checked
take
off
the

pump

cover
but
take
care
not
to
lose
the
return

spring
and

inlet
valve

ball
situated
at
the
lower

part
of
the

piston

Separate
the
throttle
chamber
from
the
float
chamber

by

removing
the

retaining
screws
leave
the
throttle
valve

intact

unless
otherwise

required

All

parts
of
the
carburettor
must
be
ctifefully
cleaned
and

sediment

gum
or

other

deposits
removed

Clean
the

jets
by
blowing
through
them
with

compressed

air
Never

push
wire

through
the

j
ts
or

passages
or
the
orifices

will
be

enlarged
and
the
calibration
affected

Check
all

parts
for

signs
of
wear
and

exchange
them
if

necessary

Examine
the
float
needle
and
seat
for
wear

and
make
sure

that
the
throttle
and
choke
bores
in
the
throttle

body
and

cover
are
not
worn
or
out
of
round
If
the

idling
adjustment

needles
have
burrs
or

ridges
they
must

be
replaced

Inspect
the

gaskets
to
make
sure
that

they
are
not
hard

and
brittle
or
distorted

Oean
the
filter
screen
if
it
is

clogged
or

change
it
if
it

is

otherwist

unsatisfactory

Check
the

operation
of
the
accelerator

pump
by
pouring

petrol
into
the
float
chamber
and
operating
the
throttle
lever

Petrol
should

spurt
from
the

pump
discharge
jet
if

the

pump
is

working
correctly
If

petrol
cannot
be

ejected
from
the

jet

when
the
lever
is
actuated
clean
the
discharge
jet
by
blowing

through
it
with
compressed
air

CARBURETTOR
Assembly
and
Installation

The

assembly
and
installation
of
the
carburettor
is
a

reversal
of

the
dismantling
and
removal

procedures
noting
the

following
points

Always
replace
the

gaskets
if

they
are
not

satisfactory
and

take
care
that
the
carburettor

linkage
operates
smoothly
and
is

not
bent
or
distorted

The

performance
of
the
carburettor
will

depend
on

the

condition
of

the
jets
and
air
bleeds
As

previously
stated
these

pacts
should
be
cleaned

using
petrol
and

compressed
air

only

Replacement
jets
or
air
bleed
screws
can

be
used
to

provide

greater
economy
or
to
increase

output
whatever
the
require

ment
When

the
carburettor
is
installed

adjust
the
idling
speed

as

previously
described

37

inter

Fig
D
7

Removing
the

pump
diaphragm
Fig
D
S
Twin

choke
carburettor

idling
adjustment

I

TJuottle

odjuJting
Jl
1l
W

2

Idling
adjust
nt

screw

t
c
l

1
cl

rf
C
L
t

0

i

I
SID

jID

L
v

i

s

A

Fig
0

9
Fast
idle

opening
adjustment

I

Choke

lever

Crank

rod

1
a
ok

arm

4

Chob
valve

5

Starring
lever

6

Throttle
ann

7

Throttle
lYl
J1e
Fig
0
10

Adjusting
the

interlock

throttle
valve

opening

J

Throttle
valve

2

Connecling
kv
r

3

Throttle

ann

4

Rocking
ann

5

Secondary
throttle
ann

6
Return

pring

38

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
ljustment
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
15

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