MG Midget Instruction Manual page 31

way.
If
this part is removed, i t affords an excellent thief proof device, hut
care should be exercised to see that it does not become chipped o r in any way
damaged, not to mention lost after it has been r,emoved. T h e ends of the
High Tension Wires are soldered to brass discs in order to make good contact
with the terminals inside the cover. See that the terminal screws are always
tight.
Misfiring may be caused by any of the following :-
l .
Dirty sparking plug.
2.
Cracked porcelain.
3.
Bad connmection to High Tension Leads.
4.
Bad connection from High Tmension Distributor to Coil.
5.
Improper adjustment of make and break points.
6.
Dirt between make and break points.
7.
Defective Coil.
These caus~es exclusively deal with the .elmectrical side. Th,ere is one other
remote cause of electrical failure, namely, bad earth contacts from the battery
to the frame. Othmer causes of misfiring can be attributed to Carburetter and
incorrect valvme adjustm'ent.
C
Engine Dismantlement. T h e removal and replacement of the cylinder
head has already dealt with but i t is perhaps advisable to describe the drive
and the timing of the overhead valve gear a little more fully.
T h e first thing that should be borne in mind is that considerable care has
been 'exercised in the design of the engine to render the operation of valve
timing as simple as possible. It must be taken for granted that the drive from
the crankshaft through the dynamo is correct, and it follows th'erefore that
when the dynamo is in a certain position there is a definite relationship
between the arms of the coupling o n the top of the dynamo and the position
of the piston in the cylinder.
T h e firing order is
1,
3, 4, 2.
When the cross head of the dynamo is in
such a position that the bolts are fore and aft and the distributor rotor is
pointing to No.
1
contact, then the engine is o n top dead centre o n No.
1
cylinder.
Thme cross head coupling attached to the dynamo is connect'ed to the
coupling driving the vertical spindle by means of laminated steel discs, and
when the overhead valve camshaft cover is removed it will be seen that there
is a mark o n the driving bevel gear wheel which meshes with the camshaft
gear wheel, and if ever the camshaft is removed, provided nothing else has
b,een disturbed, these marks only have to coincide for the timing to be correct.
It also follows that
if
on,e wants to find th.e top dmead centre to check the
ignition, o r set the High T'ension distributor, that top dead centre can be
found by turning the dynamo coupling as m'entioned above.
T h e form of coupling employed permits the cylind,er head being removed
without disturbing the timing in any way.
It is only necessary to undo two
bolts when the coupling between the dynamo and the cylinder head is dis-
engaged.