Airbox Flapper Mod
The airbox flapper is a small door on the top of the airbox which opens at higher RPMs to allow more air to flow in. It was originally added for emissions reasons, and removing it gives your bike a nice boost in throttle response time, and a little extra power. Here are the steps you need to take in order to remove the flapper, followed by a video tutorial.
Step 1: Remove Plastics
Start by removing the seat and all of the plastics from the body of the bike, including the rear fender. This will give you access to all the pieces you need to reach. After that, un clip the ECU, which is rubber-banded under the seat.
Step 2: Remove Vacuum Tube
Loosen the 3 fuel tank bolts, to gain access to the vacuum line under the tank. Trace the vacuum line from the black plastic canister (called the surge tank) to the throttle body, and remove it. You must cap this port on the throttle body (1/8”).
Step 3: Unbolt Surge Tank and Solenoid
Unbolt the black plastic canister (surge tank) and the Intake Solenoid. The solenoid is located right behind the surge tank, connected by a vacuum tube.
Step 4: Remove Flapper Solenoid
Remove the solenoid that controls the airbox flap (round silver device). Rotate it counter-clockwise and it will slide out. You can then use a small screwdriver to pry the clip on the end of the plunger off, which is attached to the flap.
Step 5: Fasten Flapper
Now that the flapper opens and closes freely, you can use double sided adhesive tape or a small screw to keep it in the open (down) position.
And that’s it! Below is a video explaining each step in detail (along with removing the EXUP device which you can skip).