O.S. Engines 86 User Manual

OPERATING INSTRUCTIONS FOR THE O.S. TYPE 86 CARBURETTOR

The O.S. Type 86 carburettor has been designed exclusively for use with the O.S. PD-02 fuel pump unit. These two components, with appropriate plumbing, form the O.S. PA-102 Pump System. The O.S. Pump Systems offer the twin advantages The Type 86 carburettor has an extra large throat, which improves breathing and increases power. With normal suction fuel

feed, or low-pressure (exhaust gas) assisted fuel feed, such a large choke area would be impracticable, but the special pump unit tive of fuel tank location or the aircraft's attitude. These qualities are especially valuable for international where it may be difficult to locate the fuel tank close to the engine. The available.

ensures

Type

increased

that

carburettor

fuel

power

delivered

and

not

the

virtual elimination

the carburettor at

suitable

for

engines

the

variation

pressure

in fuel

required

"head"

maintain

at the carburettor.

optimum

mixture strength,

class pattern aerobatic flying and in models (including scale aircraft)

not

equipped

with a pump:

for

these

the

O.S.

Type

irrespec-

carburettor

Idle Mixture

Control Screw

Mixture Control Valve Stopper

Mixture Control Valve

Nipple

Needle Valve

Plug Screw

Throttle Stop Screw

Nipple

Throttle Lever

1.5~2.0mm

Fig

Photo-1

Three adjustable controls are provided on the Type

carburettor. (See photo below.)

• The Needle Valve: For adjusting the mixture strength when the throttle is fully open.

• The Mixture Control Screw:

For adjusting the mixture strength at part-throttle and idling speeds to obtain steady idling and smooth acceleration.

• The Throttle Stop Screw: For establishing the

minimum

idling speed.

PROVISIONAL SETTING Before starting the engine, open the Needle-Valve three full turns from the fully closed position.

ADJUSTING THE CARBURETTOR

1) Set the throttle very slightly open from the idle position (see Fig. 1) and start the engine in the usual way. It is preferable to have the throttle only slightly open, to

avoid unnecessarily high revolutions when the engine starts.

2) Now open the throttle fully and gradually close the Needle-Valve until the engine is running at its maximum

speed.*

* Warning: (a) Do not close the Needle-Valve to too lean a setting,

as this will cause overheating which may result in internal damage and reduced engine life. Set the Needle-Valve approximately 1/8 to 1/4 turn open (i.e. "rich") from the peak r.p.m. setting, even though this will slightly reduce r.p.m. on the ground.

(b)

Make sure

that

the

engine

fully

"run-in"

before operating it continuously at full power. (See engine instruction leaflet.)

3) Having set the Needle-Valve as described above, close the throttle. The engine should idle steadily and continuously. (If it stops immediately, first try turning the Throttle Stop Screw clockwise a few degrees to raise the idling speed a little.) (a) If, however, the engine idles unevenly and smokes a

good deal when the throttle is re-opened, before picking up speed, it is probable that the idling mixture is too rich. In this case it will be necessary to turn the Mixture Control Screw clockwise about 5

degrees.

(b) Alternatively, if the Mixture Control Screw is set

too lean, the engine may stop when the throttle is closed, or it may idle for a few moments, then speed up very slightly before coming to a stop. Re-opening the throttle under these conditions will usually result in the engine cutting out abruptly, without smoking. Corrective action is to turn the Mixture Control Screw about 5 degrees counter-clockwise.

Mixture Control Screw adjustment is not unduly critical,

but do not turn it more than 5 degrees at a time. Carry

Dirand fibrous matter

mostly accumulate here

Photo 2

Code No.

27881400 27881200 27181600 27181620 27181610 27881100 29015019 27881330 27881120 22681953 27681340 22681953 27881300 27881800 27881810

27881820 27681900 27381940 26711305 27681970 24981837 26381501

out readjustments progressively and patiently, remembering the symptoms of rich and lean running, quoted above, until the engine responds quickly and positively to the throttle.

4) The Throttle Stop Screw is for fixing the minimum idling speed. If, after carrying out mixture adjustments, the idling speed is found to be too high, the Throttle Stop Screw should be turned counter-clockwise until the desired idling speed is obtained.

Note: Once the correct carburettor settings have been

established, it should be unnecessary to alter them. Such slight needle-valve readjustments as may be required to compensate for variations in atmospheric conditions will not normally affect the other two controls. Slight readjustments may be necessary for optimum performance if different types of fuel, glowplugs or propellers are used.

CARBURETTOR CLEANLINESS

The correct functioning of the carburettor depends on its

small fuel orifices remaining clear. The minute particles of

foreign matter that are present in any fuel can easily partially obstruct these orifices and upset mixture strength so that

engine performance becomes erratic and unreliable.

It is recommended that fuel is passed through a filter when the tank is filled and that a good in-line filter is installed between the fuel tank and carburettor and, furthermore,

that this filter is frequently cleaned to remove dirt and lint that accumulates on the filter screen. Finally, occasionally remove the needle-valve holder from the carburettor and extract any remaining foreign matter that may have lodged inside the carburettor.

PARTS LIST

Description Throttle Lever Assembly (with screw 8 lock washer) Carburettor Rotor Throttle Stop Screw Assembly Throttle Stop Screw Throttle Stop Screw Holder Ass'y Carburettor Body Carburettor Rubber Gasket Mixture Control Screw (with spring) Plug Screw (with washer) Fuel Inlet (with washer) Mixture Control Valve Stopper (with spacer)

Nipple (with washer) Mixture Control Valve Assembly

"0" Ring (S) "0" Ring (L) "0" Ring Needle Valve Assembly Needle Valve Holder Assembly Ratchet Spring Needle (with "0" ring & set-screw) "0" Ring Set-screw

The specifications are subject to alteration for improvement without notice

1986

6-15 3-chome Imagawa Higashisumiyoshi-ku Osaka 546,Japan. TEL (06)702-0225

Japan

39007

FAX.

(06) 704-2722