5) Idling System - Rotax 912-UL Repair Manual

I }.IOTE:
Generally, the main regulating system utilizes main- and needle
jets ofvarious sizes, and needles, plungers and springs ofdifferent
tlPes.
Between main jet (7) and nozzlestock (5) a washer (6) is provided which, together
with the float chamber, forms an annular gap. In particularly severe operating
conditions this ensures that the fuel is not spun away from the main jet.
A rubberring (4) seals the nozzle stock (5) off from the carburetorhousing to avoid
any fuel being drawn in via the thread and thus bypassing the main jet.
7.15.5) Idling system
During idling and low-loadrunning the throttle valve (41) is closed to such an extent
that thc air flow underneath thc plunger (19) no longer forms a sufficient vacuum.
The fuel is then supplied via an auxiliary system, the idling system, which consists
of the idling jet (8), the idling air jet LLD - no spare part - and the mixture control
screw (49) which is sealed off against the carburetorhousing by the rubber ring (9)
and secured by spring (50) to prevent it from bcoming slack. The fuel passes
through the idling jet (8) whose bore will determine the amount of fuel.
Behind the jet bore the fuel mixes with air which is supplied via cross ducts in the jet
throatfromtheidlingairchannel, the arnoUhtof airadminedbeingdetermined
by the
idling outlet bore (LA), the cross-sectional Areb of which can be adjusted by the
mixture control screw (49); it then hac?rps'tlschoke tube via bypass or transition
passages (BF), where it is mixed f,urthet with purc air.
ONOTE:
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, :
Adjusting the idling sp€ed should always be done at operating
temperaturcs. .i
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I
First, completely close the mixture'control'scnew.(49) by turning clockwise and
then open up again by the number of turas,a$,gp,apified.
INOTE:
Turning inclockwfsE'd*rectiohtrrsults in a leaner mixture and
turninganttclodsrn*,defnth*ic,henmixture.
The idling setting quoted **rr* aguide onlii'f't" optimum will generally differ
slightly. First select the desired'idling'speed,bf using the idling stop screw (45).
When subsequently adjusting,rhamixtune,control screw (49) - starting from the
basic setting - a speed drop will':be noticbd in both directions.