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3.
2
CYLINDER HEAD
(P
ISTON RING FLUTTER
)
At low speed,
the
piston
ring
is forced
against
the upper side of the
ring
groove
only
during the
intake stroke.
At
high speed,
however,
the
inertia
of
the
ring
overcomes the gas pressure and
friction,
and floats to
the
top
of the
groove
imme::liately
before the top-dead-center in
the compression stroke.
At
this moment, combustion occurs
and
the
ring
is
forced against the bottom
side of the
ring
groove
by
the combustion pressure.
This
up and down
movement
during exhaust-intake-compression
becomes
more and
more
intense,
coupled with
the increasing
inertial
force.
As this
sequence is repeated, ulti-
mately
,
the ring vibrates
violently within
the
ring
groove like a pingpong ball
between the
racket and
the
table
as
shown in
the
Fig. 3. 62
and thus
allow
the
gas
to "blow-by".
(Fig. 3. 61, 3. 62)
W.
Piston and
Piston
Ring
Disassembly
1.
Remove the piston
pin clip
and
push out the
piston
pin.
Disassemble
piston from
the connect-
ing
rod.
NOTE:
When removing
the piston
pin
clip, care
should
be exercised
so
that the
c
lip is
not
dropped
into
the crankcase.
(Fig. 3.
6
3)
2.
Remove
the piston
rings
from the piston.
If
no tool
is available,
the
rings may also be
removed with hand by separating ring at the
open-
ing with
both hands.
The ring should
not
be
twisted as
it
will
break.
fig.
3. 61
Piston
ring
motion
(i)
Exhaust
®
Intake
®
Compression
©
Combustion
®
Low speed
®
High
speed
fig.
3.
62
Piston ring flutter
(i)
Piston
®
Piston ring
Fig.
3. 63
Removing
the
piston pin clip
(i)
Piston pin clip
®
Long nose pliers
JS:
®
Rags
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