Table of Contents
Advertisement
3. 2
CYLINDER
HEAD
33
T.
Cylinder Reassembly
l.
Check
to
make sure that the
cylinder gasket
and the
two
locating pins on
the
crankcase are
installed
in place
; also check to
make sure that
the O ring is
installed
on
the
cylinder
skirt.
2.
Assemble the
cylinder
.
(Fig.
3. 55)
NOTE:
When
installing the cylinder,
check to make
sure
that
the piston
ring
gaps
are
spaced equally
apart.
This
is to prevent gas blow-by.
(Fig.
3.
56)
U.
Piston Cons
truction
The piston is
made from
select
on aluminum alloy
casting, material, SAE
332
-
T
6.
This
material
is
light
and
strong, making
it
suitable
fo
r
high
speed.
In
addition, it possess good heat conducting property
to
rapidly
dissipate the heat.
Furthermore, the
coefficient of heat expansion
is
small thus
minimizing
the warpage
at
elevated
temperature and
permitting
a
small
piston to
cylinder
clearance
design.
The
top,
compared to the
skirt,
is exposed
to
higher
temperature
and
since
the
expansion is greater,
it
is
tapered smaller toward
the
top.
The tapering
of the piston also
tends
to lessen the
piston slap
when
the
throttle is
lightly
snapped without
load
on
the
engine.
The
piston employs a four
step taper, further
the
piston pin
boss
area
is
made thicker,
resulting
in
great
er
expansion at high
temperature.
For
this
reason,
the
diameter of
the piston
skirt
is made
smaller in the direction
of
the piston
pin so
that
at the high operating
.
.temperature, the piston
will
expand into a true circular shape.
The skirt is con-
stantly provided
with flexibility to assure
that no
deformation will result
even from extended
continuous
driving.
The
piston
pin
is offset
l
mm
10.04
in) from
the
piston
centerline
in
the direction
of the
inlet valve
so
that when the piston approaches the
top-dead-
center
of the
compression stroke,
the
side
load
from the cylinder moves from the
right
side to the
left.
With a
"0"
offset,
the point
will
move to
align with the
top-dead-center
of
the compression
stroke.
As
shown in
Fig.
3. 58,
the
point
of maximum
combustion pressure occurs after the top-dead-center,
therefo
re, the purpose of the offset
is
to move
the
Fig.
3.
55
Assembling the cylind
er
CD
Cyl
inder
@
Piston
@
Piston
ri
ng
compressor
Fig.
3. 56
Avoi
d straight blow-b
y
Fig. 3.
57
Com and
tapered
shapes o
f
the
piston
(
c)
Fig.
S.
58
Offset
(D
Off-set
@
Pressure
@ Cronk
angle
Advertisement
Table of Contents
