Graves Motorsports Yamaha WR250R + WR250X Smog Block Off Kit for the 2008-2012 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.
If you are using your motorcycle on a closed course (racing, track days, etc.) you will want to remove all unnecessary equipment from your bike for reduced weight and ease of maintenance.
To get an accurate Air:Fuel (A/F) ratio when dynoing the bike. The air injection system pumps fresh air directly into the exhaust stream in order to burn off any unused fuel. Unfortunately by doing this the A/F ratio is thrown off by the extra "fresh air" in the exhaust stream. By removing the air injection system you can achieve an accurate A/F ratio. This is a "MUST" add on to achieve a proper air fuel ratio while using the Dynojet Power Commander Autotune setup.