O.S. Engines 2B Carb - 22681005 - Manual (Page 2)

Set the Needle-Valve very slightly to the "rich" side of the
peak r.p.m. setting. Make sure that the engine is fully
"broken-in" (about 1 hour of total running time in short runs)
before operating it continuously at full throttle.
II. The Mixture Control Screw is for adjusting fuel mixture
strength at part-throttle and idling speeds. Having set the
Needle-Valve as detailed above, close the throttle. The engine
should idle continuously and steadily without further
adjustment.
(a) If, however, the engine begins to idle unevenly, open the
throttle. If the engine then hesitates before picking up to full
speed, it is probable that the idling mixture is too rich. Check
this by closing the throttle again and letting the engine idle for
a little longer before again opening up. If the engine now puffs
out a good deal of smoke and hesitates or even stops, it will
be necessary to close the Mixture Control Screw. Do this by
turning it clockwise. About 5 ~ 10° turn should be sufficient.
(b) If instead of being set too rich, the Mixture Control
Screw is set too lean, the engine will stop when the throttle is
closed, or will lose speed while idling and then cut-out
abruptly (without smoking) when the throttle is opened again.
In this case, turn the Mixture Control Screw about 5 ~ 10°
turn counter-clockwise.
Mixture Control Screw adjustment is not critical and by
remembering the symptoms of rich and lean running quoted
above, it is a very simple matter to establish the best setting.
III. The Throttle Rotor Set-Screw is for establishing the
minimum idling speed. If the engine runs too fast with the
throttle closed, the Rotor Set-Screw should be turned
counter-clockwise to allow the throttle opening to be reduced.
SUBSEQUENT OPERATION AND CARE
Once the required settings, have been established it should be
unnecessary to alter them. Such slight needle-valve alterations
as may be necessary to cope with differences in atmospheric
conditions or fuels, do not affect the other two adjustments.
The engine should start readily with the throttle in the idle
position.
It is important that the carburettor operates under clean
conditions. Make sure that fuel is properly filtered before use.
We advise fitting a filter to your fuel can and another filter in
the delivery tube between tank and engine, to reduce the risk
of the carburettor jet becoming partially clogged and upsetting
running adjustments.
If dust or dirt is stuck in the carburettor causing it not to func-
tion properly, dismantle and clean the carburettor in the follow-
ing way:
(1) Loosen the lock-nut and take off the throttle rotor set
screw.
(2) Pull off the rotor from the carburettor body. Be careful
not to lose the rotor spring set in the depth of the rotor.
(3) Get the needle out of the needle valve.
(4) Screw out the nozzle-nut and push the nozzle out of the
carburettor body from the side where the rotor was set.
(5) Take off the fuel inlet.
(6) Clean the nozzle fuel inlet and carburettor body with the
clean kerosene or alcohol. After confirming no dust or
dirt is left inside of the nozzle, assemble the parts in the
opposite manner from that of dismantling.
(7) Fit the notch at the nozzle's largest diameter with the
notch inside of the carburettor body.
PARTS LIST
Description 2B
Code No.
2CA
Code No.
2CB
Code No.
2H
Code No.
Carburettor complete
R/C Needle valve assembly
Rotor stop set-screw assembly
Throttle lever
Rotor spring
Throttle lever fixing nut
Throttle fixing screw
Carburettor gasket
Mixture control screw
Fuel inlet
22681005
22681908
22681306
22681419
22481506
22481420
25081700
22615000
22481628
22681953
2248026
2268908
2268306
2268419
2248506
2248420
2508700
2261000
2248628
2268953
22481035
22681908
22681306
22681419
22481506
22481420
25081700
22615000
22481628
22681953
22781000
45181919
22681306
22781400
22481506
22781420
25081700
22615000
22781600
22681953
The specification is subject to alteration for improvement without notice.
6-15 3-chome Imagawa Higashisumiyoshi-ku
Osaka 546, Japan. TEL. Osaka (06) 702-0225
38207