O.S. engine MAX-46AXII Instruction Manual page 11

Optimum needle setting(1)
Slowly advance the throttle to its fully open position,
then gradually close the needle-valve until the
exhaust note begins to change. (4-cycle to 2-cycle)
At this point, disconnect the battery from the
glowplug, taking care that the battery leads or
glowplug clip do not come into contact with the
rotating propeller. If the engine stops when the
battery is disconnected, close the needle-valve about
30˚ and restart.
Optimum needle setting(2)
As the needle-valve is closed slowly and gradually,
the engine r.p.m. will increase and a continuous high-
pitched exhaust note, only, will be heard. Close the
needle-valve 10-15˚ and wait for the change of r.p.m.
After the engine r.p.m. increases turn the needle-
valve another 10- 15˚ and wait for the next change of
r.p.m. As the speed of the engine does not instantly
change with needle-valve readjustment, small move-
ments, with pauses between, are necessary to arrive
at the optimum setting.
Needle-valve adjustment diagram
Practical best(optimum) needle-valve setting
6
Clear, high-pitched two-stroke
exhaust note
5
Intermittent, high-pitched
two-stroke note
superimposed
on low "four-stroke"
sound.
4
Disconnect battery
leads from glowplug at
about this point.
3
Exhaust note starts to change.
Note: Although this is a two-stroke engine it fires like a
four-stroke at these rich needle-valve settings-i.e. ignition
of the fuel charge takes place at every fourth stroke of the
piston instead of at every second stroke.
20
Note :
This diagram is for reference
7
purposes only.
Maximum rpm
Actual needle positions may
setting("Lean").
differ from those shown.
1
To stop the engine, close the
STARTING
"Rich" needle-valve
throttle completely to cut off
setting when starting
fuel/air supply.
the engine.
2
The engine may stop if
the battery leads are
disconnected from the
glowplug while the
engine is running rich.
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