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22
3.
ENG
INE
Fig
.
3. 25-a
CD
Thickness gauge
@
Scr
ew
driver
Fig
.
3. 25-b
CD
Adj
usting
range
Fig. 3
.
26
Camshaft co nstruction
CD
Com chain damper ring
b
C
Fig. 3. 27
Forming
o
f
the com
@
Cam
fo
l
lowe
r shaft
@
Adjusting range
2
a
CD
Base circle
@
Ma ximum
lift
9.
Adiust the
tappet
clearance.
!Refer
to
Fig. 3.
25-o
and
b
l
111
Position
the left piston
at top-dea
d-center
on
the corr
pression
stroke, rota te
the
cam
fol
low
er
shaft so that it
is wi
thin
the
range
show
n in
Fig.
3.
25-b
.
Adjust the clear
ance
and tighten the lock
nut.
(21
Turn the crankshei
f t
through 180 ~.
This w ill
positions the
right
piston a
t
top-dead-center.
Ad iust the tappet clearance in
the
sarr.e
manner
fo
r
the lef
t
side.
REFERENCE:
Due to
the rocker fulcrum ratio
,
the clearance
at
the
valve stem is about tw ice as great as
the clear
ance at the cam fo
llow
er
surfc ce.
1
0.
Install
the cy linder head covers on bot
h sides.
E.
Camshaft Construction
In a fo
ur
stroke cycle engine the camshaft makes
one revolutio
n
for every two revolut ions of the
crankshaft.
Camshaft in
this engine
is dri ven from the crank-
shaft sprocket through a cam chain to the sprocket
(incorporat
ing
5J
cam chain damper
ring
to reduce
noise!.
(Fig.
·3. 26)
Piston top-dead-center ali
gnment marks
for both
the
inlet and exhaust
camshaf
t are
stamped
on the
right side of
the camshaft.
Further, a
tachometer
gear
box is
mounted on the right
side
of the exhaust
camshaft,
the spark advanc er and contact breaker
are mounted on the left side.
The lubricat ing oil which is pressure-fed into the
right side of the inlet camshaft is forced
out
of
the
holes
in the cam to
uniformly
lubricate the cam
surfac
e
and the rocker arm bearings.
{Fig. 3. 4,
3. 26)
The
lubricat ing oil to the exhaust camshaft lubri-
cates
the tachometer pinion, and
uniformly
lubricates
the cam surfaces, rocker
arms
and bearings.
The inlet camshaft is made of cast iron alloy with
chilled treated cam for greater
w
ear.
The exhaust
camshaft is made of high carbon steel w ith the
wear resistant alloy welded to the surface of the
cam.
Bearing contact area for both the inlet and
exhaust cams are indication heat treated
.
As the cam follower passes point "a"
shown in
fi G,
3. 27, the speed of the valve increases and
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