O.S. Engines Sirius7 FR7-420 - Manual (Page 13)

24
Start the engine.
open the throttle fully
.
Adjust the needle-valve.
Close the throttle gradually.
Set the idle speed.
Open the throttle fully.
Does the engine regain full power?
Continue running at high speed for 5 seconds.
Close the throttle.
Run at idle speed for 15 seconds.
Does the engine stop?
Apply full throttle.
Does the engine regain full power immediately?
OK
Re-set the idle speed a little higher
S
e
t
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e
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tt
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o
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in
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ea
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tra
ns
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itt
er
s
o
th
at
th
e
lo
w
es
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pr
ac
tic
al
s
pe
ed
, w
ith
ou
t r
is
k
of
th
e
en
gi
ne
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to
pp
in
g,
is
o
bt
ai
ne
d.
The position where the lowest p
o
ss
ib
le
r
.p
.m
.
,w
it
h
s
te
a
d
y
running, is obtained. Approx 40˚
open from maximum
r.p.m. setting.
Yes. No.
Yes.
One of the cylinders ceases firing.
Disconnect the glowplugs from the battery. Make sure that all 7 cylinders are firing. Make sure glowplug switch is on.
The
engine
hesitates
before
picking
up
to
full
speed,
or
appears
to
run
at
medium speed with reduced power. C
he
ck
m
ix
tu
re
ad
ju
st
m
en
t
at
id
le
speed.
Make
sure
that
all
cylinders
are firing.
Adjustment should be carried out after stopping the engine. Do not move needle-valve while adjusting other controls.
Repeat the procedure while opening and closing the
throttle until the best result is obtained.
Attention: Do not leave the battery connected while adjusting the carburetor.
One of the cylinders ceases firing.
One of the cylinders ceases firing.
25
Adjusting the mixture control valve
1.
Mixture Control Valve
Screwdriver
Turn 30
Alternatively, if the engine stops
or is slow to pick up speed,
without smoking or a strong
exhaust note, it is probable that
the idle mixture is too lean. 2.
Turn 30
In this case, it will be necessary
to turn the Mixture Control Valve
counter-clockwise approximately
1/12 turn (30 ) .
Thirdly, if the rpm increase but the engine appears to run with
reduced power, it is probable that one of the cylinders has
ceased firing. You may detect this by the difference in
exhaust note and rpm compared with previous full-throttle
running. The cutting out of the cylinder may be caused by the
idle speed being set too low or the idle mixture being too rich.
In the case of the idle speed being too low, re-set the idle
position a little higher by means of the throttle trim on the
transmitter. In the case of the idle mixture being too rich, turn
the Mixture Control Valve clockwise about 1/12 turn (30 ).
Normal safe idle speeds are in the region of 1,800 r.p.m.. 3.
NOTE:
As this is a seven-cylinder four-stroke-cycle engine,
seven firings take place every two complete revolutions.
Therefore, at first you may have an impression that the
engine is idling at higher r.p.m. than actual running r.p.m.
It is recommended to check the engine r.p.m. with a
tachometer.
Changing the make of glowplug or fuel may sometimes
require re-adjustment of carburetor throttle.
Mixture Control Valve
Carburetor Body
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburetor adjustments, it is just
possible that the Mixture Control Valve may be inadvertently
screwed in or out too far and thereby moved beyond its
effective adjustment range.
Rotate the Mixture Control Valve until its
slotted head is flush with the carburetor
body. Then, screw it in by 1mm (two turns).
This is the basic position.
If the engine hesitates, puffing
out a good deal of smoke, before
picking up to full speed, it is
probable that the idle mixture is
too rich. In this case, it will be
necessary to turn the Mixture
Control Valve clockwise to lean
the mixture. About 1/12 turn (30 )
should be sufficient.