Bentley R Type - Automatic Air Valve

TnB
TuBr
SvsrBu.
49
approximately
constant
degree
of
depression,
is
maintained
in the
region
of the
fuel
jet,
even
under
idling
conditions,
and
so
obviates
the.
necessity
f91 a
separate
idling
jet.
A
single
jet
only
is employed
in the
carburetter.
Automatic
Ain
Valve.
. .
The top
portion
of
.the
guide-spindle
cqrying
the
air
valve piston
is hollow,
torming
_a
well
surrounding
a small
siationary
damper
fiston,
suspended
from the
suction
chamber
cap by
meani
of
a^rod.
Th;
hollow
interior
of
the.
spindle
contains
a
quantity
of
thin
engine
oil,
.
and
the slight retarding
efiect
upon
the
movement
of the
alr valve
assembly,
occasioned
by
the resistance
of this
small
piston,
provides
the
momentary
enrichment
desirable
when
the
thro^ttle
is ibruptly
pPendd.
The
damper piston
is
of a
composite
construction
and
offers
little
resistance
t9
the passage
of the
oil during
the
downward.
move-
ment
of the
main piston.
EygTv
-mo1th,
as
directed
on p-agg
3o,,
the oil
reservoir
cap
nut
(8,
fig.
tef
should
be
unscrewed
and
the plunger
withdrawn,
lreat
cir,re
bging-lafen
to aaoid
damage
to the
plwngir
rof,by
bending;
the"reservoir
should
be
topped
rp,
if required,-with
the
rec-ommend"ed
oil,
so as
to
maintain
the level
of
the oil
to-the,top
of
the guide
rod
otrty.
The
plunger
slou,l$.then
b9
replaced,
taking
care
th.-at
no
dirt of grit
is
present.
-A
slight
steady pressur.e
may
6e
required
to
displace
t-he
oil
sufficientl5z
to allow
the
engagement
of the
thread
of
the
bil reservoir
cap nut.
If it
is
suspected
that
the automatic
air
valve is
not
working
c.orrectly,
the air
intake
should
be
removed,
and
a
check
made
b!
lifting
the
piston
with
the fingers,
when
it
should
be
noted
that
thb
piston
falls quite
freely
on
to-its
seat
when
released.
If any
sticking
or
sluggishness
il
apparent,
it
wil be
necessary
to
dismantle
the air
valve assembly:
firsl-Iglr.'ovq
the hydraulic
piiton
damper, next
remove
the
three
sciews
and
lift off
the
aiivalve
chimber
(1,
Fig.
14). The
piston
valve
can
then
be lifted,
oat,
the
utmost
care
being-taken
n_ot to
-bend
or damage
ct: depeyding,needle
aal,ae
(2,
Fig.
14),
or
to
bruise
the aal,ae
iry
?ny
uai.
The
valve,
dhamber
and
goid"
Jtroutd
b,e carefuttv
yry{_yit-h
a
pi6ce
of
clean
cloth
dipped
in"petrol,
and
the
piston
rod
ONLY
lubricated
with
a few
dropj
bt
tnin
bit.
,No
Pol'ishing
paste
or
abrasiaes
shoulil
be used
to
cl,ean
the
ual,ae
or
aalae
chamber.
TheSuction
disc
(5,
Fig.
14)
does not
touch
the
walls
of the
valve
chamber,
there
bping
p.
sm.all
clearance,
and
it is
centralised
solely
pf
tft. piston
rod
worklns
]tr
the guide.
Therefore,
any
sluggishneJ-s
in
movement
is
probably-due
to
dirt in
the guide,
br"on
ih"e
valve
chamber
walls.
,
When
replacing
the
valve,
it
will
be
noticed
that
there
is
a slot
wtrich.must
eng-age
a
tongue
provided
on the
carburetter
body.
The
air valve
chamber
can
orqly be
replaced
in
one
position,
th6 three
screw
holes
being
unevenly
spaced
to
ensure
thij.