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Can not use our racing mufflers
on public roads in Japan

Smog Block Off Plate Benefits

Posted by Shane McCoy on

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). These products are intended for closed course competition use only. Use of this product for any other purpose is strictly prohibited.

What is the AIS or Smog System? The air induction system (AIS) burns unburned exhaust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons.

Once these are capped off the air injection system can be safely removed. These Smog Block Off Plates are made from CNC'ed billet aluminum. Unlike cheaper clones Graves machines recesses into the caps so the OEM reed can remain in the bike and cap. There are three reasons why you want to remove the air injection system from your bike:

  • 1. 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.
  • 2. 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.
  • 3. This addition will typically remove the majority of popping on deceleration that can be experienced with un-burnt gasses within the emission charcoal chamber. Note: Proper tuning may be needed and this is general feedback.
  • 4. Greatly reduces popping on deceleration
  • 5. Reduces weight from the removal of the system

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