Secondary Air System - KTM 2003 950 Adventure Repair Manual

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Secondary air system

The secondary air system supplies fresh air to the emissions in the exhaust port, resulting in the afterburning (oxidation) of the
emissions. A line leads from the filter box to the control valve which opens as soon as the throttle valves are opened.
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The line continues to the reed valves in the cylinder heads which are actuated by the pressure pulsation in the exhaust
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system. As a result, cleansed fresh air arrives in the exhaust port. The oxygen content in the air and the high exhaust gas
temperature cause the emissions to oxidize.
If the throttle valves are closed and the engine goes into an overrun condition, the underpressure in the intake port will rise and
the control valve will close. This prevents exhaust backfire (combustion of the unburned fuel/air mixture).
The secondary air system operates in a similar manner in models equipped with an injection engine; a solenoid valve controlled
by the control unit is used instead of the control valve.
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