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Sparking Plug.
The spa.rking plug is of great importa.nce in
satisfa,ctory engine performance, and every care
should be ta,1"n to fit the correct type when re-
placements are necessa.ry.
This is Cha,mpion Type
N7, as illustrated in Fig. l2.
Remove the spa.rking plug every l,000 miles for
inspection.
IÍ the ca.rburation system is in corrat
adjustment the sparking plug points should remain
clean almost indefinitely
An over-rich mixture
from the ca,rburetter will, however, ca,use the íor-
ma,tion oí a sooty deposit on the points and, la,ter,
on the plug end ía.ce (as upper view, Fig. 12).
If
thereíore such a deposit is found, clean it oÍÏ care-
Íuny and check your carburetter.
Too high a
proportion of oil in the petroil mixture will also
cause plug íouling (see pa.ge l2).
Fig. 13.
Sparking plug gauge.
A light depsit due to any oí these ca,uses ca.n
ea.sily be cleaI]ed off, but if it is allowed to accumu-
late, particularly inside the body, the plug may
spa,rk internally with an adverse effect on the
30
engine períormance if, indeed, it does not stop the
engine altogether.
The plug should be cleaned and
tested at regular intervals, and it is suggested that
this service be performed at your garage on a. special
"Air Bla.st" service unit.
If eventua.lly the clea,ning
process fails to restore the plug to its original con-
dition of efficiency, it should be repla.ced by a new
One.
When ínspectint,Í, a pliig, also check the gap be-
tween the points.
This should be.020-.022 in. a.nd
adjustment should be ma.de by bending the side
wire (Fig. l3). Never attempt to move the
centre electrode, and it is always advisable to use
the specíal plug gap tool illustrated, obta,inable at
2/- Írom any Champíon Plug stockist or from the
Champion Spa,rking Plug Co. Ltd., Feltham. Middle-
sex.
Feeler gauges are attached to verify correct
gaP.
When refitting the plug, make sure that the
copper washer is not defective in any way.
If it
has become wom and flattened, fit a, new one to
ensure obtaining a gastight joint.
The Anial Carburetter.
The
Amal
carburetter
fitted
to
the
B.S.A.
WINGED WHEEL has been specially developed
for this type of power unit.
In genera,l it follows
the main principles embodied in the standard Ama.l
motor cycle carburetter, but it also incorporates an
automatic strangler de`tice 4, Fig. l4, which comes
into opera,tion when the throttle lever is opened
beyond its normal maiximum a.s described in page
s and l4.
This item ca.]ls íor no mainteI)ance
whatsoever, but ií the throttle slide B is removed
Íor any reason ca.re should be taken to ensure that
the small tongue at the lower end oí the strangler
.4 (not seen in the illustration), engages properly
in the groove C when re-assembling.
3l
!iill
iiliii
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