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Graves Motorsports Yamaha WR250R + WR250X Smog Block Off Kit for the 2008-2017 model bikes. Graves Motorsports Smog Block Off Plates are designed to seal off the ports on the valve cover used by the air injection system (a.k.a smog pumps or AIS).
The air induction system (AIS) burns the "unburned" exhaust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons.
Once this is capped off the air injection system can be safely removed. There are two reasons why you want to remove the air injection system from your bike.