MG MGB User Manual

B
THE IGNITION
SYSTEM
Section B.1
LUBRICATION
Distributor
CAM BEARING
Lift the
rotor
off the
top
of the
spindle by
pulling
it
squarely,
and add
a
few drops of
thin
oil
to
the
cam
bearing. Do
not
remove
the
cam
securing
screw
which
is
exposed: there
is
a
clearance
between the
screw
and the
inner
face of
the spindle for the
oil
to
pass.
Replace the
rotor
with
its
drive lug
correctly
engaging
the
spindle slot
and push
it
onto
the shaft
as
far
as
it
will
go.
CAM
Lightly
smear
the
cam
with
a very
small
amount
of
grease
or,
if this
is
not
available,
clean
engine
oil
may
be
used.
AUTOMATIC
TIMING
CONTROL
Add
a
few drops of
thin oil through the
hole
in
the
contact
breaker
base through which
the
cam passes.
Do
not
allow
oil
to
get
on
or near
the
contacts.
Do
not
over-oil.
Section B.2
IGNITION COIL
Removing
Disconnect
the switch,
contact
breaker
and HT. cables,
release
the
coil
securing
bolts
and
remove
the coil.
Testing
An
indication of the
state
of
serviceability of the
coil
may
be obtained by
assessing
the
quality
of
spark produced
by
the
coil under
test
conditions. The
test
circuit
and
equipment
are
illustrated
in
Fig.
B.1.
A5480”
'7
Fig.
B.1
Test circuit and
gap
measurement
3. SW.
contact.
4. C.B.contact.
5.
Distributor.
1.
Auxiliary electrode.
2. H.T.
contact.
B.2,
The
primary circuit
make and break
is
obtained
by
using
a
six-lobe
contact
breaker
cam
and
graduated
scale and
adjusting the
contact
breaker
gap
until
a
closed period of
between
18 and
20°
is
obtained. The
gap
must
be
accurately
set
by
using
feeler
gauges on
each
lobe of the
cam
in
turn.
The
contact
breaker lever
spring tension
must
be between
18
and
20
oz.
(510
and
566
gm.)
measured
at
the
contacts
and the
condenser
capacity .18
to
.25
mf.
The
three-point
test
gap
equipment
is
to
be connected
so
that the
auxiliary
electrode
is
on
the
HT.
side of
the
circuit.
This
electrode
causes
the
gap
to
break
down
at
low
voltage,
a
condition
used during
the
setting
of
the
gap
for
the high-speed
performance
test.
‘
The
coil
must
be
mounted
at
an
angle of
45°
on
the
test
rig
with the
CB.
terminal
uppermost
and the
coil
case
earthed.
The
mounting
angle
ensures
that
the
primary winding
take-off
to
the
LT. terminal
is
not
covered with ■uid
and
any
internal
tracking
between the
iron
core
and the
primary
lead
will be shown
up
during
test.
Earthing
the
coil
case
detects whether
or
not
short
circuits
to
earth
are
present.
High-speed
performance
test
Connect
a
peak
voltmeter
across
the
spark
gap,
run
the
distributor
at
any
speed
and then
produce
irregular
sparking
by
tapping
down
the
battery
or
by
inserting
a
resistance
in
the
primary
circuit.
Adjust the
gap
until the
peak
reading
on
the
voltmeter
is 8
kV.
Remove the
voltmeter,
and
revert to
12
volts
or remove
the
resistance
from
the
circuit.
Run the distributor
at
3,750
r.p.m.
and check the
spark.
No
missing
should
occur
at
this speed.
Low-speed performance
test
Set
the
spark
gap
to
.44
in.
(11
mm.)
and
retain
the
auxiliary electrode
in
the
circuit. The
coil should
be
at
20°
C.
(68°
F
.).
Run
the
distributor
at
100
r.p.m.
and
note
the
number
of
misses.
These
should
not
exceed
30
per
minute.
Resistance
test
Remove the
coil and
connect
a
Megger
across
the
CB. and
HT
contacts
and
note
the
reading
and then
across
the
SW.
and
HT.
contacts
and
note
the reading.
The
readings
must
be within the limits
given
in
the
‘GENERAL
DATA’.
Section B.3
'
A
U
DISTRIBUTOR
13V
The
Type 25D
distributor
incorporates
a
one-piece
body-shank
casting
which houses
the
distributor
drive shaft,
automatic
advance
mechanism,
contact
breaker
plate
MGB.
Issue5.
89961

MG MGB Specifications

General

Brand	MG
Model	MGB
Category	Automobile
Language	English