Default mixture composition screws settings in Octagon 190 engine are:
The L screw unscrewed for 50’ – 1,00’ of the clock face - 1 turn from closed position,
The H screw unscrewed for 1, 00’ – 1, 10’ of clock face from closed position.
Attention : You must not start the engine with the opening smaller than one H
screw turn (the mixture is too lean).
This setting is risky because it could lead to serious engine damage. With a correctly
warmed-up engine you should set the „H” screw in such a way that the engine could reach
maximum speed while opening the throttle completely. You should monitor the speed using
the tachometer. Next, you should unscrew the “H” screw (enrich the mixture) so that the
speed would slightly decrease (about 100-150 rpm). After performing the high speed
regulation you should not use the maximum engine power until you evaluate fuel usage and
spark plug condition and confirm that the composition of the mixture is adequate.
The composition of the minimum speed mixture is set by unscrewing the „L” screw (one
turn) and then evaluating how regularly the engine runs and the level of idle speed. Idle
speed of a properly regulated engine usually range between 2000-2200 rpm and may vary
due to temporary engine temperatures. Adjustments should be performed by means of
slight corrections of screw position (approximately the width of the slot on the circumference
of the screw head). If you observe the following symptoms: after warming up the engine
starts slowly and decreases the speed steadily until the cut out, it floods the spark plug, and
at the same time the slight opening of the throttle makes it easier to start it – you should
make the idle speed mixture leaner by screwing the “L” screw and you should make another
attempt after re-warming up for about 1 minute on medium speed.
If the engine works with large fluctuations on low speed, and it has strong vibrations on idle,
you should slightly unscrew the „L” screw, increasing throttle’s opening by screwing the
throttle buffer screw in order to increase the idle speed.
The symptoms of too rich mixture at idle speed are the following: after starting the cold
engine it works properly for a while and when the temperature increases it starts to work
slower and slower until it cuts out. Opening the throttle before the cut-out increases the
amount of fumes, and the engine reluctantly gains speed. After a while on high speed
(4000-5000 rpm) the engine takes low speed again, but left on it for a short time its speed
would decrease systematically until the cut-out.
Another symptom of too rich idle speed mixture: the engine works properly on low speed in
low temperatures (e.g. right after the start) and has very low speed and tendency to cut out
after warming up significantly (2-3 minutes on minimum 6000 rpm speed).
Engine with too rich idle speed mixture very often starts reluctantly when hot. At the same
time, it starts much better with the throttle opened a little. Sometimes starting the hot
engine without opening the throttle just a little bit may be impossible. In any of these cases
you should make the mixture leaner by screwing the “L” screw slightly.
2016-06-22
