In this tutorial, we learn how to replace the stock air filter on a Ninja motorcycle. Start off by opening up the air box using an Allen wrench. After this, take the bolts out of this and set the air box cover down. Now, remove the air filter to see how dirty it is. If the air filter is full of residue, then you need to change it! Now, clean the inside of the air filter area with a wash cloth . After this, replace your new air filter back into the right spot. Next, apply the filter cover back on, along with the bolts. When finished you will have a fresh air filter, making your bike much more gas efficient.