Sas Valve - APRILIA SX 125 Service Station Manual

RX SX 125
•
Before riding the bike for the first time;
•
Each time the engine has been operating with an empty oil reservoir;
•
When the lubrication system components have been replaced.
In order to bleed the oil pump and pipes, open the oil bleed screw (5).
Drain the oil until it is completely air-bubble free.
Once the oil is fully bubble free, close the bleed screw (5) again.
With the engine running, check the delivery pipe to see if the oil pump is working properly.

SAS valve

In order to control CO and HC emissions in vehi-
cles without a lambda probe, exhaust fumes un-
dergo a post-combustion process as ambient air
(rich in O2) is supplied to the flow of burned gases .
This system is particularly necessary when the en-
gine is idling and at the warming up stage as, given
these conditions, the catalytic converter is not able
to activate the post-combustion reaction freely.
Thanks to the secondary air system - SAS-, the
post-combustion reaction is immediately activated
outside the combustion chamber, reducing CO
and HC first, and thanks to the heat produced, it
accelerates the thermal adjustment of the catalytic
converter. The SAS takes advantage of the pres-
sure fluctuation at the exhaust.
At the low-pressure stages (when cleaning), the
exhaust sucks in fresh air from the secondary air
system; the unburned gases leaving the combus-
tion chamber, warm and still active, continue and
complete combustion when in a highly oxidising
environment.
At the excess-pressure stages, the secondary air
(reed) valve closes the circuit, thus blocking return
flows.
The secondary air valve is fitted with a cut-off de-
vice, activated by a low-pressure intake on the inlet
manifold. This device cuts off the circulation of
secondary air when released to avoid excess lean-
Engine
ENG - 127