O.S. Engine MAX-75AX-BE Instruction Manual - page 17
32
MIXTURE CONTROL VALVE ADJUSTMENT
With the engine running, close the throttle
and allow it to idle for about five seconds,
then open the throttle fully. If ,at this point,
the engine hesitates to pick up with thick
sound, the mixture is too rich. Correct this
condition by turning the Mixture Control
Screw clockwise 15-30 degrees.
If the mixture is excessively rich, the engine
may stop suddenly before picking up when
the throttle is fully opened, or with prolonged
idling the engine r.p.m. will drop gradually
and the engine stop.
If, on the other hand, the mixture is too lean,
the r.p.m. will not increase with a weak
sound or drop after increasing for a short
time and stop. In this case, turn the Mixture
Control Screw counter-clockwise 90 degrees
to positively enrich the idle mixture, then turn
Note: Mixture Control Valve adjustments
should be made in steps of 15~30
degrees initially, carefully checking
the effect, on throttle response, of
each small adjustment. Carrying out
adjustments patiently until the
engine responds quickly and
positively to the throttle control.
If the mixture is excessively lean, the r.p.m.
will increase gradually, then the engine stop.
the screw clockwise gradually until the
engine retains full power cleanly when the
throttle is reopened.
33
REALIGNMENT OF MIXTURE CONTROL VALVE
SUBSEQUENT STARTING PROCEDURE
Once the optimum needle-valve setting has
been established (see page 30, Needle-valve
adjustment diagram) the procedure for starting
may be simplified as follows.
Open the needle-valve 1/2~1 turn 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, take the same
procedure. Needle opening may vary to
temperature, humidity and season.
1.
2.
3.
Mixture Control Valve
Carburetor Body
Rotate the Mixture Control Valve until its
slotted head is flush with the carburetor
body, then screw it out one turn.This is the
standard position.
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.
Screwed out
one turn.