Gravely 424 - Cylinder Head

Valve
Clearance:
Valve
clearanee
must
be
checked after resurfacing
and lapping
in. Install
valves
in
guides,
rotate
eamshaft
:o
position
where
cam
has
no efiect
on tappet
-
hold
valve
ffrmly
on
seat and
check
clear-
anee between
valve stem
and
tappet
(See
Clearance
Section).
Adirrstable
tappets
are used.
Loosen
the
locking
nut, turn
adjusting
nut in
or out
until
proper
clearance is
at-
tained then securely
tighten
loclcnut.
CYLINDER
HEAD
Blocked
cooliag ffns
often
cause
localized
trot
spots-
which
can result
in
"blown"
clinder
head
gaskets.
If
gasket
fails in
atea surrounding_one
of
the retaining
capscrews,
high
temperature
combustion
gases
cip burn
away
po:tions
of aluminum
alloy'head.
If
no
evidence
of this
is found"
head
should
be checked
for flatness.
A
slightlv warped
head
can
be
resurfaced
by simply
rubbing
it on
a
piece
of
sandpaper
positioned
on a
fat sur-
face.
Carefully
clean
carbon deposits
from
cylinder
head if
it is to be
reused
-
rr*
putty
knife or
similiar
blade
to scrape
deposits.
Be
careful not
to nick
or
scratch aluminum,
espeeially
in
gasket
ieat area.
RING
GEAR
If inspectioa
of the ring
gear
reveals
broken" exessively
worn or
otherwise
damaged
teeth, the
ring
gear
must be
replaced.
The ring
gear
is
press
fftted into
a recess
on
the
outer
perimeter
of
tl* ny*fr*t.
fhe
flywheet
must be
oS &e
engine for
ring
gear
replacement.
Sever:rl
methods
may be
used
to
remove the
damaged ring
gear.
One
method is to
breat<
the
gear
u,ith
a
cold
chisel and/or
a hack
saw. Another
way
is to he*t
the
ring
gear
with
a torch,
then drive
the
gear
ig tt
"
flywheel.
If
the
latter
method
is used,
the fywheel
will
also
absorb
some heat
and it
must be
allowed
to
cool
before
the
new ring gear
can
be installed.
-
The new
gelr
must
be expanded
rvith
heat
before
installation,
This
can be
done by
srrbmerging
the
gear
in
hot oil
or herrting
in
oven
to about
400 to 450oF.
Position
the heated gear
on the
fywheel,
then
after iraking
sure
it is not
cocked, either press
the
gear
on with
an arbor
press
or
drive
it
on
with a
soft-head
hammer.
As thi
gear
crxrls,
it
will
contract
to form
a tight press
fft on the flywheel.
Be
sure to
tighten
the flywheel
retaining
nut to
the
proper
torque value
after reinstalling
the flywheel
on
the
engine.
DYNAIJIIC
BATANCE
SYSTEIvI
The
Dynamic
Balance
System
is
standard
on the C-gZ
(K-gZl)
engine.
On
eonventional
single
clinder
engines,
counterbalancing
is by
necessity
a compromise.
The counterweights
are
designed
to balance
only
about
Ll2
of the
inertial force
created by the
reciprocating
weights
such
as
piston,
piston pin,
etc.
The reason
for
this
is that this
force
varies from
0 value
whenlhe piston
is
midway in
the
cyl-
inder
to
maximum
force
when
the
piston
reaches
TDC
and BDC. If
the
counterweights
were
designed to exacily
balancc
the
maximum
force,
they would
in e$ect
create an unbalance
each
time
-the
counter*elgt tr rotate
to
{'
and l80o positions
when
the inertial
force
drops to
zero.
By
designing
the counterweights
to
qptit
the force,
vibration
is lcept
within
acceptable
limits
for most
applications.
The Dynamic
Balance
system
cnhsists
of two
balance
gears
which
run
on needle
bearings. The
gear-bearing
units are
assembled
to
two
stub
shafts which
are
press
fftted
into
special bosses
in
the
".onk"uru.
Snap ring
re-
t{ners hold
the
gea;s
and
spaoer washer
*u .,rud
to control
end
piay.
The
gears
are
driyen
ofi
the
crankgelr
in
the direction
opposite
to rotation
of
the crankshaft.
Operation:
The
balance gears
function
to oppose then
add
to the
force
exerted by the
eounterweights
to e$ec-
tively
reduce
vibration.
As shown in Figure
34A,
the reciprocating
weights
are exerting
maximum
force
(indi-
cated
large
arrow)
in the vertical
direction
shown
while
the counterweights
exert
force
(indicated
small
arrow)
in
the opposite
direction.
In this
position,
the balance gears
each
add force
to the force'of
the
counterweighti
u