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GENERAL
DESCRIPTION
The
crankcase
is
made
from
high-grade
aluminium.
It
is mounted
on
a rigid aluminium
base
rvhich forms
the oil
sump. In
the
base
is fltted
a
trough into
which
the dippcr
on
the
end
of the
connecting
rod
dips at
each
revolution.
This trough is kept
at
constant level
by oil bein[
fed
through
metering
holes
which
connect
to
the
main
sump.
The crankshaft is
made
of high quality
steel,
and
is
carried on
taper
roller
or
ball
bearings of large dimensions. The
crankshaft
and connecting-
rod
assembly are
very
carefully
balanced.
The connecting-rod
is stcel
with
a
phosphor bronze small-end
bush.
The
big-end
is
split
and
fitted with white
metal
steel backed
shells.
The
piston
is of die
cast
aluminium
alloy.
It
is
fitted with
compression
rings, one
o{
rvhich
is a
special
taper
chrome-plated
ring
and
must
be
fitted
in
the top
groove
with the
fåce marl<ed
TOf
uppelmost, and
an
oil
scraper
rirq
above
the
gudgeon
pin.
Drain
holes
åie drilled
in
the
bottom ring
groove
The
gudgeon
pin is
located
by a circlip at
each
end and
ls {ully
floating
in
the
gudgeon
bosses.
The cylinder is
madc
from
close
grained cast
iron
and
is provided with
circumferr:ntial fins
of
special shape
for
cooling.
The cylinder
head
is
made
from an aluminium alloy,
deeply {rnned
to
assist
cooling.
It
is
detachable
and fitted
with a
§asket-wirich
forms
thc joint
betrveen
the cylinder
ancl
head.
The camshait
is
made
from
meehanite
alloy, and is driven
by
heavy
spur
gears.
'lhe
pinion is
rnachined
from
steel
and
meshes
with
the
camshaft.
The inlet and
exhaust,cams operate
directly on the tappets.
Tappet
adjustment is
effected
by
the
fitting of
difierent
thicknå§s
discs
uiråer
tappet
heads. fhc
whole
of the
cam gear
is
encloscrl
and
running in
oil.
Lubrication is
by
JAI'
pa.tcuted
dipper
system
and
is
entirely
automatic
and
-very
eihcient,
_affording
ample supply
to all
working
parts.
'fhe
crankcase
is-
provided
with the
well-known
]AP
vacurrru System
and
crankcase release,
ensuring
a
clean engine and
economy
in
oil.
The th.rottle
is
operated
by a
centrifuga,l
governor.
A
hand
operated
choke,is
fitted to facilitate starting
when
engine
is
cold.
A centrifugal
governor
is driven by
a spur
wheel meshing
with the
cam-
shlft
and.
operates.the
throttle by
simple
mechanism.
A
slow running
and
starting
lever
is fitted,
which
is
operated against
the
governor
arrn.
Peen
2
The flywheel
Ian is of
cast
iron
and
is fitted directly
on
the
cranksheft.
The cooling
air
is supplied
by this
fan, which
creates
a draught over tho
cylinder
head
and portions
of the
cylinder, which are correctly
flnned
for this
purpose.
These
fins
should
be kept
clean
for
efficient
cooling.
The cowl
is
designed
to
give a cooling draught
to the
necessary
portiont
of the cylinder
and cylinder
head.
The
oil filler
cap on the
side
of the
crankcase
is of the
screwed
type.
Attached
is a
dipstick, having
high level
mark. THE
DIPSTICK
tsOTTOM
END
INDICATES DANGER
LEVEL.
ALWAYS
XNBP
MOVE THE
CAP WHEN
THE
ENGINE
IS
RUNNING.
The
engine
base
must
be
standing
level when checking
or re-filling
oil.
A
carburetter
has been
specially
designed
for
each
engine.
The
setting of
the jets should
not
be
interfered
with
except
by
an experienced engineer.
It
is
correctly set
at the
works, and any
slight alteration may
upset the
smooth
running
of the
engine.
Jets,
fi,lters,
etc., may
occasionally
require
cleaning
to
remove
dirt
or
water.
This
can
be
simply
done
by
blowing air through
them.
See
pages
22
to
25
for
maintenance and
carburetter parts list.
The damper on the governor arm is
to
prevent
hunting by putting
extra
friction
on
the spindle. Great
care, however,
must
be exercised
in
adjust-
ing
this,
as
too much
friction will
prevent the
throttle
opening
fully.
lVhen
commerclal petrol ls
used,
lt
le advlsable to add
one
table-
§poon
of
eng,lne
otl wlth
one
gallon of
fuel.
Thta should be well
mlxed.
COLD §TARTING.
(")
Open
petrol filter tap by turning
in
anti-clockwise direction.
Each
filter
is fitted
with
a tap which
requires
to
be
screwed
either
fully in for OFF, or fully out for
ON,
to
ensure
leak proof
operation.
(å)
Slip the
slow
running
lever
into
position
to partly
close
the
throttle.
(r)
Push
the carburetter air
choke
levcr to
close
choke
for
cold
starting
only.
Turn
engine
slowly
until
compression
is felt.
When
compression
is felt, give the starting
handle
a
sharp
pull
in
wpwørds
direction.
IMPORTANT.-Always pull starting
handle
up
smartly
to start;
do
not attempt to start by
continuous
turniag.
When
engine has
started
release
the
slow
running
lever.
When
engine
commencss
to
pick up
speed,
puli
the Carburetter
air
choke
lever forward
to
open
choke.
HOT STARTING.
To
facilitate
restarting
a
hot
engine
a
release
tap
has been
provided
on
the
inlet pipe.
When
starting difficulty
occurs, open
the tap
and
rotate
the
crankshaft slowly
a few
times
to
clear
the induction
system of excessively
rich mixture.
During
this
operation the
throttle
should
be
left
wide
open.
The
air
choke
should
be
left
open
at
all
times
for starting hot
engines.
With
the tap
still
open,
crank
engine
to start in
the usual
manner. A{ter
engine
has
started
and
is
running
evenly,
close
the tap to
prevent
weakening
of
the mixture.
(d)
(r)
U)
(g)
Pecn
3
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