41
PERIODIC
SERVICE
CARBON REMOVAL. - Regular
removal
of
carbon
deposits
from
the.
comhustion
chamber
helps
to
keep engine
effi-
ciency high.
Thefrequency
with which
it
is
advisable to
remove
carbon
will
vary
considerably with the type of fuel used, the type of oil used,
and operating conditions. Use
of
highly leaded gasoline
necessitates
frequent
removal
of'
carbon
and lead deposits
from
the
cylinder head,
top of piston and valves, and top
surface
of the
cylinder
block.
V ALVE GRINDING. - Valve grinding
is
a
service
that
should be done if
your
plant
is
to continue running efficiently. When-
ever
the engine begins to
lose
power
or
to
use
more
fuel
or
oil than
it
normally does, check the
compression
to
determine
the need of
repairs.
Check the
compression
of
each cylinder with a
reliable
compression
gauge while the engine .is 'still
warm
and
as
soon
after
stopping the
en-
.
gine
as
you can. The
compression
of each cylinde;r in a new engine
at
sea
level
is
about
90
lbs~
at
hand cranking (105
lbs.
elec.
cranking)
speed.
Compression
readings
of
the
cylinders
should
be
within
10
lbs.
of
each other and high enough to
assure
no
loss
of
power. A
low
com':'
pression
reading
may point to a poor valve condition, worn
or
sticking
piston
rings,
worn piston
ring
grooves,
or
worn cylinder
walls,
An
excessively high
compression
reading
may point to a heavy
carbon
for-
mation within the
cylinders.
If
readings indicate a
compression
loss,'
remove
the
spark
plugs and
squirt
only enough
SAE
number
50
au
into each cylinder to
seal
the
rings.
Take the
compression
readings
again.
If
the
readings
remain
about the
same,
the valves probably need
servicing.
However, if the
readings
have
increased
quite a bit, the
valves
are
probably in good
condition •
.
Loss
of
compression
may be due to worn
or
sticking
piston
rings,
worn
piston
ring
grooves,
or
worn cylinder
walls.
Follow
instructions
given
in the Maintenance and
Repair
sect~on
when making
repairs.
CRANKCASE
BREATHER VALVE. - If
the
engine begins to leak
oil,
. . the valve in the
breather
tube
may
besticking
..
Lift
the
rubber
cap
from
the
breather
tube. Then lift
out
the valve and inspect
it.
Frequently the
breather
valve
(check
valve)
will' lift off with and
remain
inside the
rubber
cap.
Pry
it out.
First·
. !
. I
soak
then wash the valve in
kerosene
or
suitable
solvent
so
thatthe
disc
.1
.............
·
will work
freely.
Run the engine and hold
the
valve
assembly
in place
to prove
it
opens and
closes.
Replace a faulty valve with a new one.
If
the
metal
mesh
type baffle,
used
in
the
breather
tube of
later
engines,
is
completely
restricted
by sludge,
etc.,
lift
it
out with a hooked
wire,
"
clean and
reinstall
it
or
a new one, leaving only
2-114"
of empty
space
....
_
..••...
J
inthe
top of the
breather
tube.
Avoid
crushing
the baffle
or
allowing
..
shreds
to
fall
into
the
crankcase.
An
internal
retainer
ring
stops
the
.
baffle from falling through.
Reassemble
the valve
as
illustrated.
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