O.S. Engines 21VZ-B V-Spec - Manual (Page 23)

Finally, beyond the nominal break-in period,
a slight readjustment toward a leaner needle
setting may be required to maintain
maximum performance.
CARBURETOR CLEANLINESS
The correct functioning of the carburetor
depends on its small fuel orifices remaining
clear.
REALIGNMENT OF METERING NEEDLE AND
MIXTURE CONTROL VALVE
In the course of making carburetor
adjustments, it is just possible that the Metering
Needle and the Mixture Control Valve may be
inadvertently screwed in or out too far and
thereby moved beyond its effective adjustment
range.
The basic positions can be found by rotating
the Metering Needle until its slotted head is
flush with the ball link body.
Mixture Control Valve
Carburetor Body
Rotate the Metering
Needle until its slotted
head is flush with the
ball link body. This is the
standard position.
Metering Needle
Ball Link
Carburetor Body
Slide Valve
First rotate the Mixture
Control Valve until its slotted
head is flush with the
carburetor body. Then screw
the valve in exactly 1 turn.
This is the standard position.
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