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Cylinder Head and Piston.
Before removing the cylinder head the sparking
plug should be taken out, and examined for condi-
tion as described on page 80'
To remove the head.
unscrew the four huts A, Fig. ll, putting these on
one side carefully together with the saddle washers
B.
Then lift the head clear of the barrel and re-
move the carbon from its inner surface by means
of a suitably shaped tool, bearing in mind that the
head is made of aluminium alioy' and is therelorc
comparativeiy snft and easily damaged by careless
use of the decarbonising tool.
It is particularly
important in this respect that the joint face C.
which makes contact with the cylinder barrel.
should not be scratched or otherwise damaged. or
the running of the engine will be impaired.
Turn the engine until the piston is at the top of
its stroke (Lt. at the outer end of the cylinder),
and then carefully remove the carbon from its
surface in the same way as described {or the head,
noting that the piston is also of aluminium, anti
therefore equally liable to suffer damage if not
carefully handled.
Special Note.—In normal circumstances there
is no need to disturb the cylinder barrel when
decarbonising, although it will be noted that it is
free to slide off when the head is removed.
If the barrel Should be disturbed at the crankcase
joint when. removing the head, remake the joint
using a new paper washer and a very smali quan-
tity oi jointing ccmpouud.
The joint between head
and barrel is metal to metal and requires no gasket.
or jointing,
There is, however, no Objection to
the use Of a reiiabie jointing compound on this
joint if preferred.
After decarbonisation in the manner described,
the engine can be re-built without difficulty. Care~
fully slide the cylinder head into position. by allowing
28
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