9.
REMOVAL
OP
ROCKER
BOX,
CYLINDER
HEAD
AND
CYLINDER
BARREL.
It
is
not
possible
to
remove
the
rocker
box
oul)'
whilst
the
engine
is
in the
frame
but
the
cylinder
head
and
box
must
be
removed
as
a unit.
Remove
carburetter attached
to
induction
stub
by
two
bolts.
Remove
exhaust
pipe
or
complete
exhaust
system
in
one
piece.
Dis-
connect
oil
feed
pipe
and
exhaust
valve
lifter
cable
from
rocker
box.
Check
that both
valves
arc
seated
and
remove
sparking
plug.
Unscrew
the
four
cylinder
head
nuts, lift
the
head
clear
of
the barrel spigot and obtain
assistance
to
hold the push
rods
and
cover
tubes
whilst
withdrawing
the
head
from
the
other
side.
Make
sure that the rubber
and
composition
washers
from
the
endc;
of
the push
rod
cover
tubes
are
not lost
and
remember
to
keep
the
inlet
and
exhaust push
rods
separate
for
rc-fitment.
Remove
the nine nuts
holding
the
rocker
box
to the
cylinder
head
and
withdraw
the
box
from
the studs. This will
enable
the
head
nuts
to
be
withdrawn.
Revolve
engine
till piston
is
at the bottom
of
stroke
and
remove
cylinder barrel ( this
need
not
be
done
at
every
decarbonisation
as
piston
top can be
cleaned
with barrel in
position.
Cover
crankcase
mouth with
rag
to prevent
ingress
of dirt or
foreign
matter.
10.
REMOVAL OP VALVES FROM
CYLINDER
BEAD.
Compress
valve
springs with a suitable type
of
valve
compressor.
When
springs are
compressed
the
valve
cotters
will
fall
from
the
valve
stems.
Remove
valve
compressor.
Remove
valves.
Remove
valve
springs and
collars
from
valve
spring compartment.
Remove
carbon
from
underside of
valve
heads.
DO
NOT POLISH
VALVE
STEMS.
Check
valve
stems
in
guides;
if
free,
do
not
touch
guides,
unless
they
arc
badly
wom.
If
guides
and
valves
show
no
signs
of
exces-
sive
wear,
re-grind
valve
scats.
Always
grind the
seats
when
new
valves
arc
fitted.
11.
GRINDING
OP
VALVE
SEATS.
Use
as
little grinding
compound
as
possible.
Place
valve
in guide and grind lightly, using
a screwdriver or hand
vice.
Do not
revolve
valve
a complete turn, but
oscillate,
frequently raising
valve
from seat and
placing
in a different position.
Do
not over-grind
valve
seats
(a
wide
seat
is
not
necessary).
When seat
is
ground sufficiently, that is,
when
the marks of the grinding make a com-
plete ring on the seat and on the
valve,
remove
all
signs
of
grinding paste
from
seat,
valve
and
valve
pockets.
If the
valves
or the seats are badly burnt
or pitted,
it
may
be impossible to obtain a
perfect seat by grinding. The seat
will
then
have
to be re-cut, and the
valves
re-faced, or
new
valves
fitted.
12.
Fl'ITING
OF
VALVES.
Thoroughly clean
valves,
seats, and
valve
pockets.
Fit
valve
springs and collars.
Lubricate
valve
stems.
Fit
valves
into guides, compress
valve
springs, and
fit
cotters.
If the
valve
cotters are greased with a thick
grease,
the
grease
will
hold the cotters in
place
. until the springs are
released.
10
:;.
REMOVING
AND
RE-FITTING
OF
VAL VE
GUIDES.
Valve
guides
are a driving
fit
in the cylinder
barrel or head.
To
remove,
tap
O\lt
with a double diameter
drift.
Use the drift to replace or
fit
new
ones.
Seats must be trued-up with cutter after
refitting of guides, to ensure that the guides
and
seats
are in alignment.
14.
Fl'ITING
OP
CYLINDER
BARREL,
CYLINDER
HEAD
AND
ROCKER
BOX.
Position piston rings
so
that
gaps
are equally
spaced.
Lubricate rings, barrel and piston, and rotate
engine
till piston
is
near top of stroke.
Fit paper washer to crankcase mouth, ensur-
ing that cylinder oil
feed
hole
is
unobstructed.
Fit barrel
over
piston and slide right
home.
Clean
faces
of rocker
box
and head
and
smear
with jointing compound. Having
placed
the cylinder head nuts in position, push rocker
box
home
on head and
fit
all nine nuts and
washers.
These arc probably better tightened
when
head
is
fitted to engine.
To Next Page
Loading...
