Fig. 7
-5
4
Fig. 7-55
Fig. 7-56
Fig. 7-57
ENGINE
MAINTENANCE
-
Top
End
Maintenance,
Piston
and
Piston
Ring
Maintenance
.
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Back
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Pre
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SidP cl
ea
rance
when
p i
sto
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f
lL1
dl
S rn
1l
1P
direction
o f
t
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rr
ow .
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Side
cl
ea
r
anc
e
when
pis
ton
fl
oa
is
in
the
di
r
ect
io
r)
o f
t
he
a
rr
ow .
Tefl
on
coating
•
•
7-5
PIS'fON
AND
PISTON
RING
MAINTENANCE
(GP338,
GP433B)
7-5-1
The L
-s
haped
piston
rings
featuring
the
following
three
improvements
:
( 1 )
Better
sealing
(2)
Higher
output
(3)
Improved
radiant
efficiency
7-5-2
•
Remove
the
piston
ring
from
the
piston,
and place
it
in
the
cylinder
so
that
it
is
in
t
ig
ht
contact
with
tne
cylinder
wall.
By
using
the
piston
head,
position
the
ring
in
parallel
to
the
cyl ind
er
top
edge. Measure
the
ring
end gap
with
a
feeler
gauge.
If
the
gap measured is in
the
range
of
0.0012
to
0.002'' (0.3
to
0.5
mm),
the
ring
is
in
satisfactory
condi-
tion.
If
more
than
0.002'' (0.5
mm),
the
ring
face
is
excessively
worn.
Remove the
ring
from
the
cylinder
and keep it
in
a free
po
sition
.
Then,
measure
the
ring
end gap.
If
the
gap
measured
is
less
than
0.0012''
(0
.3
mm),
the
ring
is
con-
sidered
to
be
fatigued
with
heat. Replace
it
with
a
new
one;
ott1erwise,
power
loss
or
ring
breakage
may
result.
When
installing
a
ring
on
the
piston,
avoid
opening
the
end gap
a
part
more
than
0.627''
(1
6
mm),
because
the
ring
may
break.
Fig.
7-58
7-5-3
In
addition
to
the
description
referring
to
the
judgement
of
the
condition
of
piston
rings,
the
following
check-ups
should be made:
(1) Check
the
piston
ring
for
sticking
to
the
piston
groove.
(2) Check
for
scuffing
by
the
piston
rings.
(3) Check
the
piston
ring
face
for
contact
with
the
cylinder
wall.
(4)
Check
the
piston
ring
bottom
for
con1act
with
the
groove
.
•
-95-
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