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3. 2
CYLINDER HEAD
23,
at a certain
point (reversal point) the
movement
stops and
then
starts to
recede.
At
point
"b
",
the
movement of the
valve
is at a standstill.
The
tappet
clearance should
be adjusted
between
points
" a
" and
"c "
on
the
base circle.
The base
circle
on this model
camshaft
is
larger
in comparison
to the other types, providing
a
smaller
unit load
on
the contact
surface
of the
cam
follower.
The tappe
t
clearance for cold setting is
0.03
mm
(0. 00
l
2
in) between
the cam and
the
cam follower.
This
provides
a
clearance
of
0.05mm (0.002inl
between the
com
follower
and
the
valve
stem.
If
it
is
considered
that the
point
of valve
open-
ing
is
when the
valve
has
been lifted
l.
0
mm
lO.
039
inl and
that point
of
valve closing
is
when
the
valve
has
been
closed to
less
than 1. 0
mm
(0.
039
inl
lift,
the valve
operating
sequence
diagram for
this
model engine
wi
ll
be
as
shown
in
the
figure
at
the
right
(fig.
3.
28
1
.
The angle is
in
reference
to the crankshaft
rotation.
The
tappet adjustment at cold setting
is
considered
to
have
been
set
to 0.03mm
(0.012inl
clearance
.
Under this
condition,
the
de
sign
tappet clearance
is
con sidere
d
to be
zero
and
the lift to
be 1.
l
mm
10. 043 in}. wit
h
a
cold
setting
.
F.
Cam follower
The cam
fo
llower
arm
is
located
bet
we
en
the
cam
and
the
val ve,
and
transmits
the
motion of
the
cam to the valve by pivoting at
the
cam
follower
shaft.
(fi
g.
3.
29)
Ignition timing
2000 rpm-5'
3400 rpm· 40
'
Fig
.
3.
28
Val
ve
timing
CD
Top
dead
center
@
Exhaust
valve
®
Intake
va
lve
openi
ng
(z)
Intake
va
lve
clos ing
®
Crankshaft rotatio
n
CD
®
Igniti
ng
period
©
Intake valve
®
Exhaust valve closing
@
Exhaust
valve
opening
@)
Bottom dead center
Fig. 3.
29
Com-Valve mechanism
CD
Cam
followe
r
®
Cam follo
w
er shaft
©
Outer torsion
bar
@
Torsion
bar
valve spring
®
Outer
arm
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