O.S. Engines 65AX - Manual (Page 17)

32
REALIGNMENT OF MIXTURE CONTROL VALVE SUBSEQUENT STARTING PROCEDURE
Once the optimum needle-valve setting has
been established (see page 29, Needle-valve
adjustment diagram) the procedure for starting
may be simplified as follows.
Open the needle-valve one half-turn (180
degrees) from the optimum setting.
Set the throttle one-quarter open from the
fully closed position, energize the glowplug
and apply the electric starter. When the
engine starts, re-open the throttle and re-
adjust the needle-valve to the optimum
setting.
When re-starting the engine on the same
day, provided that atmospheric conditions
have not changed significantly, it may be
practicable to re-start the engine on its
optimum(running) setting.
Note:
1.
2.
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. The
basic position can be found in the sketch shown below.
Mixture Control Valve
Carburetor Body
Rotate the Mixture Control Valve until its slotted head
is flush with the carburetor body. then screw it in 4/5
turn (290 degrees). This is the standard position.
Screwed in 4/5 turn
(0.4mm)
When an optional extra in-cowl type E-4050 silencer
is used, screw in the Mixture Control Valve 5/8 turn
(230 degrees) from the position where its slotted
head and carburetor body is flush with.
33
SUBSEQUENT READJUSTMENT
Once the engine has been run-in and the
controls properly set up, it should be
unnecessary to alter the mixture settings;
except to make minor adjustments to the
Needle-Valve occasionally, to take account of
variations in climatic conditions. The use of a
different fuel, however, particularly one
containing more, or less, nitromethane and/or
a different type or proportion of lubricating oil,
is likely to call for some readjustment of the
Needle-Valve. Remember that, as a safety
measure, it is advisable to increase the
Needle-Valve opening by an extra half-turn
counter-clockwise, prior to establishing a new
setting. The same applies if the silencer type is
changed. A different silencer may alter the
exhaust pressure applied to the fuel feed and
call for a revised Needle-Valve setting. The
use of a different glowplug may also require
compensating carburetor readjustments.
CARBURETOR CLEANLINESS
The correct functioning of the carburetor
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.
O.S.'Super-Filters'(large and small) are
available, as optional extras, to deal with this
problem. One of these filters, installed on the
outlet tube inside your refueling container, will
prevent the entry of foreign material into the
fuel tank. It is also recommended that a good
in-line filter be installed between the tank and
needle-valve. Do not forget to clean the filters
regularly to remove dirt and lint that
accumulate on the filter screen.
Also, clean the carburetor itself occasionally.