MG Midget J1 1933 Instruction Manual page 39

Misfiring may be caused by any of the following
:-
l.
Dirty sparking plug o r plugs.
2.
Bad connection to High Tension Leads.
3.
Bad connection from High T'ension Distributor to Coil.
4.
Improper adjustment of o r burnt make and break points.
5.
Dirt between make and break points.
6.
Defective Coil.
These causes exclusively deal with the electrical side. Th,ere is o n e o t h e ~
remote cause of electrical failure, namely, bad earth contacts from the battery
to
the frame. O t h e r caus'es of misfiring can be attributed to Carburetter and
incorrtdt valv,e adjustment.
Engine Dismantlement. T h e removal and replacement of the cylinder
head has been already dealt with but it is perhaps advisablse to d,escribBe the
drive and the timing of the overhmead valv'e gear a little mor'e fully.
T h e first thing that should b'e 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 f r o m
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 p i g o n in the cylinder.
T h e firing order is
1, 3, 4, 2.
W h e n the cross head of th'e dynamo is in
such
n
position that the bolts are fore and aft and the distributor rotor is
pointing to N o .
1
contact, th,en the engine is o n top dead c,entre o n N o .
1
cylinder.
T h e 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 b,evel gear wheel which meshes with th,e camshaft
gear whe,el, and if ever the camshaft is removed, provided nothing else has
been disturbed, these marks only have to coincid,e for the timing to be correct.
It also follows that if o n e wants to find the top d'ead centre to check the
ignition, o r set the High Tsension distributor, that top dead centre can b e
f o u n d by turning the dynamo coupling as msentioned 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 t o undo two
bolts when the coupling b'etween th'e dynamo and th'e cylinder head is dfs-
engaged.
Timing Dismantlement.
T h e following operations will deal with a
number of parts, such as
Oil
Pump, High Tension Distributor, Brackets, and
dismantbement of Timing Gears, prior to dealing with the most important
subject of ,engine knowledge, namely lubrication. All the various parts are so
co-related in the case of the Midget Engine that the description may appear
to be somewhat disjointed, but it will be found that the illustrations will
materially assist and are in fact mor'e informative than any amount of text.
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