?
7
1
he piston rod sliding within its he:~ring is the only part wllich is in actual
contact nith any other part, the suction piston
and
its needle possessing
a
cle:~r:~nce space round them. If, therefore, the piston does not return re:~dily
to its seat it is proh:tble that the piston rod has become dry or sticky.
'1'0
free this, remove the
oil
cap nut to he found at the top
of
the suction
cllamher, pour in a few drops
of
good quality thin oil-such as sewing
nlachine oil-and replace the cap. In p:lrticul;ir obstinate cases a little
p:~r:lffin may be introduced into the
oil
cap opening and the piston worked
up and down until it is free by inserting a fineer in the air inlet. Under no
circrcinsta~~ccs .\11o~~ld a Izcai~\.-/~odi~d llrhrica~~t sz~ch
ns
cnfii~~e oil
be
~~srd,
(111~1
110
oil
INILS~
hc
infrod/~c~~~l
011
a71y ofh('r Dart of the srcction chant her.
Water or
Dirt,
If
this is suspected, with a small article-such as
a
pencil
raise the piston so that the jet can be seen.
Flood the carburetter ny
holding up the float-chnntber needle and observe
if
the petrol issues freely
from the jet.
If
it does not
do
so there is foreign matter of some sort blocking
the p:lssnge to the jet.
To
rectif! tllis, start the 'engine and open the throttle,
then n?oment:~rily block the air inlet by placing the hand over it, keeping
the throttle open until the (engii~e commences to race.
'This trouble is not
a
frequent one with the
S.tT.
carburetter owing to the
size
of
the jet and petrol passilges.
When it does occur, however, the foreign
matter can usuall!
be cleared h\ the foregoing treatment.
If
it is not, the
only alternative is to remove the jet, hilt flzis erficdicwt sltoz~ld
012
110
accoll~it
17c rcsortcd to ~r~rlcsc the 171ct110d olrtli?~cd 110s failcd
to
cffcct
u
ci~,aroiice cr11~1
it
is ah.\oll~tciy Izecc\.\arv to do so.
Removing the Jet.
If
it is necessar, to remove the jet the exact position
of
the jet :~djusting nut should Erst be noted.
A
file mark on one
of
the
hex:lgons will f:l.cilit:~te this. Then disconnect the control le~er. The jet
:~djusting nut should now be screwed home to its top position, carefully noting
the
number of turns it has been given. It can then be removed by unscrewing
the jet holding screw-the upper large hexagon head nearest to the carhuretter
body-after uncoupling the jet controlling lever.
When refitting the jet it has to he very c:~refully centred so that the needle
is exactly in the centre of the jet opening, hut it is practically impossible
correctly to centre this
part unless it is thoroughly understood how this has
to he carried out.
Replacing and Centring the Jet,
It n~ust be understood that, although
the ncedle is very ne:~rly ;is l~rgc ns the jet orifice within which it works, yet
it must on no :~ccount touch at any point.
Replace the jet, t:~king cnrc that th<e parts are nssenhled in their correct
position (see Pig.
35).
Having done this, feel
if
the piston is perfectly free by raising it with the
finger.
If
it is not, slacken the jet screw
a
frwtion
of
a turn, screw up again,
xnd try the piston again. It may be necessary to slacken the jet several times
before the piston is finally perfectly free.
As soon as the piston is free the
jct adjusting nut can he screwed h:lck to its orirpr~ul po\itloi~ (see Adjusting).
PACE
FIFTY-EI(;HT
1)
/
1
To Next Page
Loading...
