O.S. Engines 32SX-MX - Manual (Page 15)

◆ If the needle-valve is closed beyond the optimum
setting, the model will slow down, accompanied by
visibly diminished exhaust smoke. In this case, im-
mediately throttle down and return the model to
shore. Re-open the needle-valve approximately
one-half turn and repeat the runs until the optimum
needle setting is found.
◆
◆
◆
◆
Aim to have the model achieving its highest perfor-
mance after the engine has consumed about one
quart of fuel. Having found the optimum needle-
valve setting, make a note of the number of turns
necessary to re-establish this from the closed posi-
tion.
With the engine run-in and the optimum needle-
valve setting determined, the mixture control valve
should be checked as follows:
Launch the boat and gradually open the throttle to its
fullest extent. If at this point, the engine puffs out a
good deal of smoke and does not accelerate smoothly
and rapidly, it is a sign that the idling mixture is too
rich.Therefore, turn the mixture control screw clock-
wise 45 to 60˚. Repeat the run and recheck the result.
◆
If, on the other hand, the idling mixture is too lean,
the engine is likely to speed up momentarily, then
cut out abruptly when the throttle is re-opened. In
this case, first turn the mixture control screw coun-
ter-clockwise 90˚ to make sure that the mixture has
become richer, then make incremental adjust-
ments, each way, until an acceptable balance be-
tween rich and lean settings is achieved. Carry out
these adjustments patiently under actual running
conditions, until the engine responds quickly and
positively to throttle movements. Use a small
screwdriver to adjust the mixture control valve via
its slotted screwhead in the center of the outer end
of the throttle rotor.
With the optimum mixture control valve position,
light smoke is visible during high-speed running
and engine rpm increases smoothly during acceler-
ation. Remember that, if the engine is operated
with the fuel/air mixture slightly too lean, it will over-
heat and run unevenly or cut out. As with all en-
gines, it is wise to set both valves a liitle on the rich
side of the best rpm setting, as a safety measure.
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