APRILIA PEGASO 650 STRADA, Service Station Manual

Page: 175 / 236

chamber, reducing CO and HC first, and thanks to
the heat produced, accelerating the thermal ad-
justment of the catalytic converter. The SAS takes
advantage of the pressure fluctuation at the ex-
haust. At the low-pressure stages (when clean-
ing), the exhaust sucks in fresh air from the
secondary air circuit; the unburned gases leaving
the combustion chamber, warm and still active,
continue and complete combustion when in a high-
ly oxidising environment. At overpressure 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-
ing of the exhaust fumes that might cause bursts
in the muffler which may damage the exhaust
valves and the catalytic converter. When riding,
the valve remains closed.
At low rpm, the valve is activated to reduce carbon
monoxide emissions.
WHEN ADJUSTING CO DEACTIVATE THE SECONDARY
AIR SYSTEM AS THE EXHAUST FUMES DILUTED BY THE
SYSTEM DISTORT THE READING OF THE CARBON MON-
OXIDE PERCENTAGE.
SEE THE CO ADJUSTMENT SECTION TO DEACTIVATE
THE SAS.
AFTER ADJUSTING CO, REMEMBER TO RESTORE THE
SECONDARY AIR SYSTEM AS THE VEHICLE WORKS
REGULARLY ALSO WITH THE SYSTEM DEACTIVATED
BUT, GIVEN THESE CONDITIONS, THE HARMFUL EMIS-
SIONS INCREASE. LACK OF AIR CIRCULATION MAY AL-
SO RESULT IN OVERHEATING AND THIS IN TURN COULD
DAMAGE THE SAS COUPLINGS AND PIPING.
TO BLOCK AIR CIRCULATION USE SUITABLE SYSTEMS
ONLY; USING PLUGS TO BLOCK THE AIR INTAKE IN THE
FILTER HOUSING MAY DAMAGE THE SECONDARY AIR
SYSTEM DUE TO OVERHEATING. IF YOU FORGET A
PLUG FITTED, IT MAY GET INTO THE INTAKE DUCT WHEN
THE VEHICLE IS USED, THUS BLOCKING THE THROTTLE
VALVE AND RESULTING IN LOSS OF CONTROL OVER
THE VEHICLE.
PEGASO 650 STRADA - TRAIL - FACTORY
Engine
ENG - 175