4.22
CARBURATION AND FUEL SYSTEM
9923412 - 2012 Sportsman 400/500 and EFI Tractor Service Manual
© Copyright 2011 Polaris Sales Inc.
500 H.O. INTERNATIONAL EMISSIONS SYSTEM
Overview
International model ATVs are equipped with an emissions system from the factory. The emission system is designed
to meet the various international emissions standards.
The emissions system consists of:
• A. Air Valve Filter
• B. Air Valve Assembly (one way operation)
• C. Tubing
• D. Air Injection Tube
• E. Catalyst
The emissions system utilizes an air valve filter (A), one-way air valve system (B), and vacuum to help reduce emissions.
The air valve assembly (B) contains a vacuum shutoff. When engine RPM drops quickly or is at high RPM, the air valve
closes. During idle through mid-range RPM the air valve is open and air is drawn into the from the PVT intake duct.
The air valve assembly (B) opens and closes based on the vacuum pressure connected to the air duct.
The exhaust pipe creates a vacuum after each engine exhaust pulse. The air valve (B) opens and closes based on this
engine pulse. Fresh air then travels through the air injection tubes (C and D) and into the exhaust. This air (oxygen) enters
the exhaust pipe and mixes with the exhaust gases from the engine, reducing emissions. The air and exhaust gas mixture
then passes through the silencer (E), which contains a catalyst. This catalyst also reduces emissions by interacting with
the exhaust as it passes through the silencer. NOTE: No maintenance or service of the catalyst is required.
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