O.S. Engines 21RZ-R (P) - Manual (Page 17)

REALIGNMENT OF MIXTURE CONTROL VALVE ■
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.Its basic
position can be found by first rotating the Mixture
Control Valve until its slotted head is flush with the
carburettor body. The valve is then screwed in exactly
1 turn to re-establish its neutral position.
Mixture Control Valve
Carburetor Body
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.
BEFORE STARTING THE ENGINE
1.
2.
Before starting the engine for the first run of the day,
remove the glowplug and check the engine by
rotating the flywheel by hand. It should rotate
smoothly. Now turn the engine with an electric
starter until fuel is drawn into the carburetor. At first,
rotation may feel 'sticky' due to oily residue
remaining within the engine. The engine should
rotate freely after fresh fuel has been drawn into the
working parts.
Check the glowplug. If the plug element is distorted,
off center, or has a white appearance, engine
performance may be below par. With racing type
engines, glowplugs have to be regarded as
expendable items. Therefore, replace the plug if
necessary.
3.Reinstall the glowplug and start the engine.
4.When re-starting the engine, turn the flywheel by
hand, as before (but without removing the glow-
plug) to make sure that there is nothing unusual,
before energising the glowplug and applying the
starter.
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