Table of Contents
Advertisement
The exhaust valve opens
50°
before
the
piston
reaches the bottom
dead centre, and
clos~s
10°
after
the piston passes the upper dead
centre
whi-ch
is exhaust
closing lag. The
~xhaust
duration is also
240°.
The
above timing values are giv:en
for
the theoretical clearance
between
the valve
stem and the
rocker
end
equal to 2
~~·
.
Tlhe
correct valve bmmg
IS
ensu-
red by matching, during
assembling,
the
marks
on
timing
pinions
2
(Fig.
9) and
4.
Valve
Adjustment
The
n ormal
oper
ation of
the
en-
gine depends to
a great
extent on
the size
of
the
expansion
clearance
between
the
valve stem
and
the
rocker
end.
When
checking or adjusting
the
clearance,
place
a tray
under the
cylinder head, remove the
cylinder
head
cover
and
drain the oil
that
has
accumulated. Set
i:he piston
to the
Fig.
s.
Valve
timing
diagram
upper
dead
centne
of
the com-
pression
stroke,
turn
the crank-
shaft so that the mark "B"
on
the
flywheel
is matched with the
mark
on the crankcase.
In
doing
so, observe through a sight hole
in
the
crankcase,
after first removing
the rubber p lug. In
this
position,
the
both
va lves
will
be
completely
closed,
whereas
their
rockers
must
freely
swing
on their
pins. Then,
using
a
flat
feeler gauge,
check the clearance
betw.
e
en the
both
·rockers and
the
valves.
If
the clearance
is
found to be
incorrect,
slacken
·check nut
24
(Fig.
7)
and,
by
rotating adjusting bolt 23 in
one
direction or the
other,
obtain the
required
clearance.
Thi
s
done, tighten up the check
nut. The clearance is adjusted on
a cold
engine and
must
be
equ
al
to
0.07
mm.
If
the clearance is absent or too small,
the valve wi ll
not fit
closely
to its seat
at the
moment of
closing;
if the
clearance
is too l·arge,
the valve opening
will
be delayed.
The
clea rance
value should be ·checked whenever required when
checking
the
clearance
in
the
other cylinder turn the
cr
ankshaft
through
360°
an
d proceed
with
checking and
adjusting
as
it is
des-
cribed
above.
Care
of Valve Timing Gear
In
case
knocking
of
the
valves
increases,
check and a djust the
clearances
between
the va lve stem (cap) and the rocker end.
It must be borne in
mind that on the air-cooled
engine
the ope-
ration
of valve
gear drive is
well
audible owing to the
absence
of
a
26
Hide quick links:
Advertisement
Table of Contents
