MG MGB User Manual

D
THE FUEL
SYSTEM
tank and
pipe
lines
are
entirely
free from
any
kind of
foreign
matter
or
sticky substance
capable
of
causing
this
trouble. /
Needles
Remove
the
piston
and
suction
chamber
assembly.
Slacken
the
needle
clamping
screw,
extract
the
needle and check
its
identifying
mark
(see ‘GENERAL
DATA’). Re■t the
correct
needle,
ensuring
that
the shoulder
on
the shank
is
■ush with the
piston
base.
Piston
sticking
The
piston
assembly comprises
the
suction
disc
and the
piston
forming
the
choke,
into
which
is
inserted the
hardened and
ground
piston
rod
which
engages
in
a
bearing
in
the
centre
of
the
suction
chamber and
in
which
is, in
turn,
inserted
the
jet
needle. The
piston
rod running in
the
bearing
is
the
only
part
which
is in
actual
contact
with
any
other
part,
the
suction
disc,
piston
and needle
all having
suitable clearances
to
prevent
sticking.
lf
sticking
does
occur
the
whole assembly
should be
cleaned
carefully and
the
piston
rod
lubricated
with
a
spot
of thin oil. No
oil
must
be
applied
to
any
other
part except
the
piston
rod. A
sticking
piston
can
be
ascertained by
removing
the
piston
damper
and
lifting
the
piston
by pressing
the
piston
lifting
pin;
the
piston
should
come up
quite
freely and
fall
back
smartly
onto
its
seating
when
released.
On
no
account
should the
piston
return
spring
be
stretched
ot
its tension
altered
in
an
attempt to
improve
its
rate
of
return.
Section
05
AIR
CLEANERS
The
air
intake
■lters
are
of the dry
paper
element
type
requiring
no
attention
between
■lter replacement.
The
air
filter
casings
should
be
removed and cleaned
out
periodically
to
remove
any
dust deposit.
Filter
replacement
Disconnect
the
engine
rocker
cover
breather
pipe
from
the
front
■lter
(early cars).
Unscrew
the bolts
securing
each
air
■lter
to
the
choke bracket and
■xing plate
respectively and
remove
the ■lters
from the vehicle complete.
Remove
the base
plate and
throw
away
the old
paper
element.
Clean the inside
casing
and intake tubes
thoroughly and reassemble,
using
new paper
elements.
Section
D.6
CARBURETTERS
(S.U.
Type HIF
4)
IMPORTANT:
The
instructions given in
this
section
for
adjusting, dismantling and
reassembling the
carburetters
apply
only
to
cars
not
fitted with exhaust
emission
control
equipment.
Carburetters ■tted
to
cars
with exhaust
emission
control equipment
must
be
tuned
and
serviced
in
accordance with the
instructions given in
Workshop
Manual
Supplement AKD 4957.
Tuning/adjust
Before
tuning
the carburetters
in
an
endeavour
to
rectify
poor
engine
performance,
check the following
items
to
ensure
that the maladjustment
or
fault
is
not
from another
source.
Valve clearance
Spark plug
condition
Contact breaker
(dwell angle)
Ignition
timing
and advance
Presence of
air
leaks
in
the
induction
system
Operation of
engine
controls.
g.
Compression
pressures
I")??ng
Carburetter
tuning is
con■ned
to
setting
the idle and fast
idle
speeds, and
mixture
at
idle
speed.
To achieve the
best
results,
a
reliable tachometer,
a
balancing
meter
and
an
exhaust
gas
analyser
(CO
meter
of
the
infra-red
non-dispersive
type
or
equivalent)
are
required.
The
instruments
are
essential when
tuning
vehicles
equipped
to
conform with exhaust
emission
regulations.
1.
Remove
the
air
cleaners
as
detailed
in
Section
D.5.
2.
Check
the throttle for
correct
operation
and
signs
of
sticking.
3.
Unscrew
each throttle
adjusting
screw
until
it is just
clear of
the throttle
lever
stop
when
the throttle
is
closed,
then
turn
each
screw
one
turn
in
a
clockwise
direction.
4. Raise the
piston
of
each carburetter,
using
the lifting
pin, and check that
the
piston
falls
freely
onto
the
bridge
in
the
carburetter
body when the
lifting
pin is
released. If
the
piston
tends
to
stick,
the
carburetter
must
be
serviced.
5. Remove
the
suction
chamber
assembly, and lift
the
piston
clear of the
bridge,
so
that the
jet
is
visible.
6. Turn the
jet adjusting
screw
of each
carburetter
until
each
jet
is
■ush
with the
bridge
in
the
carburetter
body
or
as
high
as
possible
without
exceeding
the
bridge
height.
.Ensure
that
both
jets
are
in
the
same
relative
position
to
the bridge
of their
respective
carburetter.
7. Check
that the
shoulder of
each
needle
is
■ush
with
the
underside of
its
respective
piston.
8.
Turn the
jet
adjusting
screw
of each
carburetter
two
turns
clockwise.
9. Turn the fast
idle
adjusting
screw
of
'each
carburetter
in
an
anti-clockwise
direction
until
it is
well clear of
itsfast
idle
cam.
10. Re■t the
suction
chamber
assembly.
11. Unscrew
and withdraw
the
piston
dampers
from
the
suction
chambers.
Top
up
with
new
engine
oil
(preferably
S.A.E.
20)
until the
level
is
%
in.
(13
mm.)
above the
top
of
each hollow
piston rod
(see
Fig.
D.
13).
Refit
the damper
assemblies.
MGB.
Issue
5.
86842

MG MGB Specifications

General

Brand	MG
Model	MGB
Category	Automobile
Language	English