MG MGB - Page 115

THE FUEL SYSTEM
4NC06I
Fig.
D.
17
Carburetter
reassembling
(S.U. HIF)
77
showing
1. Checking
that
the point of the
float
(arrowed) is
0.04
i
0.02
in.
(1.0
t
0.5 mm.) below
the
level of
the ■oat chamber
face.
NOTE:
It
is
only
necessary
to
carry
out
the following
timing
check
if the
cause
of the carburetter
malfunction
which
necessitated
the
dismantling has
not
been located.
73.
74.
75.
76.
77.
78.
79.
Temporarily
plug the
piston
transfer
holes.
Fit
the
piston
into
the
suction
chamber
without
its
spring.
Fit
a
nut
and
screw,
with
a
large ■at washer
under the
screw
head,
into
one
of the
suction
chamber ■xing
holes,
positioning the washer
so
that
it
overlaps
the
chamber
bore.
Fit the
damper
and washer.
Check
that
the
piston
is
fully
home
in
the
suction
chamber,
invert the
assembly
to
allow
the chamber
to
fall
away
until the
piston
contacts
the washer.
Check
the
time
taken
for
the
chamber
to
fall
the full
extent
of
the
piston travel;
the
time
taken should
be
4
to
6
seconds.
If
the
times
are
exceeded, check
the
piston and
suction
chamber
for
cleanliness
and
damage. If after
rechecking
the
time is still
not
within
these limits,
renew
the
suction
chamber
and
piston
assembly.
Reassembling
80. Reverse
the
procedure
in 39
to
79,
noting
the
MGB.
following:
a.
The
throttle
spindle
must
be fitted
with the
threaded
end
at
the
piston
lifting
pin
side of
the
body.
b. Ensure
that
the
throttle
disc
is
■tted
in
its
original
position;
over-run
valve
at
the
top
of
the
bore
and
its
spring
towards
the
inside of
the
carburetter when
the throttle
is
closed.
Issue2. 91427
3.5
piston.
C.
2.
Needle
guide
etch mark aligned
correctly with
iston
transfer
holes.
houlder of
needlealigned
with
underside face of
New throttle
disc
retaining
screws
must
be used
when
re■tting the
disc. Ensure that
the throttle
disc
is
correctly positioned and
closes correctly
before
tightening the
retaining
screws.
Spread the
split ends
of
the
screws
suf■ciently
to
prevent
turning.
Position
the throttle
spindle end
sealsjust below
the
spindle housing ■ange.
The
starter
unit
valve
is
■tted
with
the
cut-out
towards the
top
retaining
screw
hole
and
its
retaining plate
is
positioned with the
slotted
■ange
towards the
throttle spindle.
When ■tting
the
jet
assembly
to
the
adjusting
lever
ensure
that the
jet
head
moves
freely
in
the
bi-metal
cut-out.
After
■tting
the ■oat
and valve,
invert
the
carburetter
so
that
the
needle
valve
is
held
in
the
shut
position
by the weight of the ■oat
only.
Check
that the
point
indicated
on
the
■oat (see
illustration)
is
0.04i0.02
in.
(l.0i0.5
mm.)
below the
level of
the ■oat-chamber face.
Adjust
the ■oat
position
by carefully
bending the brass
pad. Check
that
the
■oat
pivots
correctly
about
the
spindle.
Check
that the small
diameter
of
the
jet
adjusting
screw engages
the slot
in
the
adjusting
lever
and
set
the
jet
■ush
with the bridge of
the
body.
Use
a
new
retaining
screw
when re■tting
the
needle and
ensure
that the
needle
guide etch
mark
aligns
correctly
with the
piston transfer
holes (see
illustration).
After fitting
the
needle
assembly,
check that the shoulder of
the
needle
aligns
the
under-side
face of
the
piston.
D.l9