"Monobloc" Carburetor - BSA B31 Instruction Manual

fig. l6h,
'Monobloc'
cafturetter
40
tho
piston
is at t.d.c, on
the
coEpression stroke, i.e,,
with
both
valves closed. This will plevent any
pressure on
the valves dudng
the operation,
Prelimfuary Work,
It
is
6rst
ne4essary
to
rcmove
the
pehol
tank. Turtl
of
the petrol
tap
aDd detach
the
oehol
pip€.
The tank is
secured
to
the frame by a
bolt
through the
steering head lug
and
two
bolts
to
spe.ial
lugs at the rear of
the
frame top tube.
Whe[ thestbolts
are removed
the
tank
can be taken
ofl.
Note the
corect
order of
the rubber mountings for
reassembly
purposer.
On swinging arm models.
First
remove the Detrol tank
strap which is
located under lhe front of
tbe tank
aDd is
held
in
position
by two duts.
The central
taDk
locking
bolt can then be removed when the rubber cover
in
tha
top of
the tank
is
pulled otr
Next
detach
the high tenrioa lead and
iemovo
thc
sparking
pl'lg.
Disconoect
tle
steadyiDg
ståy from
the
cyli[der
head
to
the frame,
aDd then take offcarburetrer
by æmoving the air
nange
nuts,
(When fitted with
an
air-cleaner
see
page 35.)
By unscrewing the ring
out at
the
top
of the carburetter
the slides carl be
pulled
dght out
and
tied to
the
frame
top
tube
out of
the
way, while the main body of
the
instrument
can
be
removed,
Take
oare
trot
to
damage th€
carburetter
flange washer,
The pipe
atrd siletrcer can be
removed complete, the
pipe
itsef
b€iDg
a push fit in
the
cylinder
head.
Remoyiog the Cylinde.r
H€ad. (For
Coop.
and Gold
Star
models
see
pages
48and
50
&spectivelr.
DiscoDne4t
the
oil
fe€d
pipe to thc rocker spildles
aDd the
oil retu$
pip€
ftom
the
rocker box
to
tåe
crankcase. Note that
t-h€
union søews for
the
oil pipe
to
the rocker
spiadles have
a m|rch smaller hole in
the side than the union
screw for.
the
retum pipe--€ point
to re4ember
when reasseEbling.
The
exhaust valve lifter
cable cao either
b€ discoDoectcå.
or the
exbaust rocker box cover
removed
leavilg
the
cable
htact.
Remove
the inlet
valve
rocker box
cover.
SlackeD the castellated
glald rut
secudng
the pulh-rod
cover tube
to
the
qylitder
head (usiDg
the
sp€cial
.C'
,iil
jrl
Ne q@
ry,
t
t
,t
t