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Cylinder Head and Piston.
Beíore removing the cylinder head the spa,rking
plug shou]d be taken out, and examined íor condi-
tion as described on page 30.
To remove the head,
unscrew the four nuts Á, Fig. 1I, putting these on
Óne side carefully together with the saddle washers
B.
Then lift the head clea,r of the barrel and re-
move the ca.rbon írom its inI`er suría,ce by means
oí a suitably shaped tool, bearing in mind tha.t tho
head is ma,de of aluminium alloy and is thereíore
comparatively soít and easily damaged by careless
use oí the decarbonising tool.
It is particularly
importa,nt in this respect that the joint ía.ce C,
which makes contact `rith the cylinder barrel,
should not be scratched or otheririse damaged, or
the running of the engine will be impa.ired.
Tum the engine until the piston is at the top oÍ
its stroke (t.¢. at the outer end oí the cylinder),
and then careíully remove the carbon from itr
ëurface in the sa,me wa,y as described for the head,
noting tha,t the pistoli is also oí aluminium, aad
thereíore equally liable to sufíer da.mage iÍ I}ot
carefully handled.
Special Note.-In normal circumsta.nces there
is no need to disturb the cylinder banel wheI]
decarbonising, although it will be noted that it is
Íree to slide oÍ-f when the head is removed.
If the barrel should be disturt)ed at the crankcase
jojnt when removing the head, remake the joint
usíng a new paper washer and a very small quan-
tity of jointing compound.
The joint between head
and barrel is metal to meta] and requires no ga.sket,
or jointing.
There is, however, no objection to
the usc of a reliable jointing compound on this
joint if preferre(l.
Aítcr decarbonisation in the manner described,
the engine can be re-built without difficulty.
Care-
íully sli(le the cylinder hea,d into position by allowing
28
the íour long studs to occupy their proper positions
between the appropriate pairs of fins, and then
repla,ce the four saddle washers B, followed by the
nuts J4.
Note that the fins nearest the brake drum
are shorter and its head must be fitted the correct
way round.
Tighten the head nuts evenly, a little
at a time and do not use undue force.
Refit the sparking plug, having satisfied yourself
that it is ili conect working order a,s described,
and filia.lly replace the silencer and exhaust pipe,
not forgetting the flange jointing washer.4, F'ig. IO,
which must be renewed if it is damaged in any
Wa:y-
The engine is now ready íor immediate service.
Check the cylinder head nuts, inlot manifold nut8,
carburetter clip and exhaust pipe mts, aíter the
ongïne has run for a short time and settled do`mi.
Fig. ]2.
Sparkinc,c,,plug.
29
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