must be replaced. When ordering valve seats, state the
size
-
besides the part No.
-
as in the case of the jcts.
Treat-the central float with every care when disman-
tling the carburetter. If the two bodies are displaced
in relation to each other or the link
(9)
lifting the float
needle or limiting the stroke (10) distorted, the fuel
level is no longer as required for a proper functioning.
At the top of the jet holder, the needle jet (11) and at
the bottom the main jet (12) are screwed in place.
Wear limit for needle jet and stepped needle is
30,000 km.
The diagrammatic representation shows the arrange-
ment of ducts in a horizontal sectional view (Fig. 122).
6.1.3. Trouble Shooting
and
Tuning
The appearance ol the sparking-plug is always and ex-
clusively decisive for carburetter tuning. The interiur
of the sparking-plug must be light sand-coloured.
Light, because the additives included in the two-stroke
engine oils prevent the deposition of products of com-
bustion not only in the engine but also in the interior
oi the sparking-plug to a large extent. If the specified
sparking-plug
hl
141260 shows heavy beads with
a
normal driving performance, do not use a sparking-
plug with a higher thermal value but find the cause
and remove it.
Do
not extremely change the basic carburetter tuning
by reboring the jets but take into consideration all
factors associated with the function of the carburetter
and restore the latter to the standard condition.
In the case of s i g n
S
o
f
o v e
r
h e a t i n g, the fol-
lowing is involved:
a) Air leaks in the intake socket between carburetter
and cylinder (insulating flange, packings).
b) Air leaks in the induction systeq
-
filter box leaky.
Filter is seated near the centring edge. Rubber
suction tube defective.
c) Paper element of the filter damaged due to improp
er handling, therefore unobstructed air passage.
The opposite, namely,
f
e e d i n g t o o
r
i c h a
m
i
X
t u re
,
as indicated by the appearance of .the
sparking-plug (with normal carburetter tuning!) may
be due to the following faults not caused by the car-
buretter:
a) Paper element of the air filter dirty (clean by
tapping) or wet, therefore, no or a reduced air
passage. Paper filters that
have become wet are
useless in spite of their impregnation.
b) Silencer (especially its tail piece) clogged by de-
posits left after
corribustion.. The back pressure
be-
comes higher than permissible, burnt residual gases
remain in the cylinder (poor degree of filling). Due
to-a retarded combustion the sparking-plug appear-
ance shows a dark colour.
c) The specified mixing ratio of
33:l was not observed
and 25 :l used.
A
n
o r m a l f u e l f
e
e d is a prerequisite for prop
er carburetter function! Therefore, before any car-
buretter re-adjustments take place, pull the petrol-
resistant hose from the nipple of the carburetter and,
by opening the fuel shut-off cock for a short time,
check that a sufficient supply of fuel is ensured. If this
is not the case, any adjustment at the carburetter is
useless. Normal rate of flow through the filter cock is
about 12 1 in 60 min.
Causes for a reduced rate of flow may be:
a) Vent hole in tank cap closed by preserving agent
or polish.
b) The ports drilled through the rubber packing were
compressed by tightening the two screws of the
retaining disk at the filter cock too much or thq
were partly obstructed by abraded material.
The fuel passing through may suffice for half
throttle, for full throttle the output drops or the
engine stalls because the float chamber of the car-
buretter is almost empty.
c) Due to an additicn of graphite or MoS, prepara-
tions to the fuel, the inlet filter at the fuel shut-off
cock is clogged by deposits. This will also result
in an insufficient supply of fuel
-
see above!
Trouble shooting in the carburetter
should be started with checking the partial load need!e
position. For normal operating conditions. the needle
positions 2 to
4
are sufficient (see setting table). But
one should not proceed without discrimination; it is
always the appearance of the sparking-plug that is
decisive for the selection of the needle position. Thus,
it may be possible, to use ne,edle position 5 for the
running-in period and then position
4
in order to en-
sure optimum operating conditions.
The correct setting also is the most economical!
With
a setting for an extremely lean supply, you have to
shift gears earlier and more frequently (inclination
to
pinking)
-
this will cost you fuel!
A resilient double plate, the needle holder, guides and
retains the partial-load stepped needle. For setting take
care that the l o
W
e r p l a t e (A) is used as reference
in connection with the notch to be used (to be counted
from top to bottom). The upper plate engages with the
notch above the selected one.
When mounting the needle holder with stepped needle
take care that the former fully contacts the bottom of
the throttle valve, otherwise there will be setting er-
rors (difference in level) or the partial load needle may
be deformed.
Float bodies distorted due to improper
treatment can be aligned by means of easily made
control devices. Either prepare a U-shaped wire stir-
rup or a sheet-metal template of the desired dimen-
sions. If a vernier caliper is available, use it for taking
measurements.
For checking, unscrew the needle jet carrier and hold
the carburetter in the way shown in Fig. 125. Measure
at the point indicated by the arrow.
A uniform distance of anything between 0.3 to 0.5 mm
must be present between the two float bodies and the
ruler (see arrow). If this is not the case, realign the
valve lever (A) as required. This measure must be ad-
hered to because the correct fuel level is dependent
upon it; below 27 mm there is the risk that the floats
contact the carburetter casing and. consequently, fuel
flows over the carburetter.
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