How do I clean the air filter(s)?
Air filters should be cleaned according to the schedule in your bike's owner's manual, which is at 500 miles, then 6000, then every 6000 thereafter, or more often if operating in dusty conditions or stop-and-go traffic; elements should be replaced after 5 cleanings or 20,000 miles, whichever comes first. Cleaning more often will not hurt anything, and it's probably worth cleaning the filter any time you have the tank off.
A dirty air filter element will cause the bike to run richer (less air), reduce the fuel economy, and potentially cause other problems associated with running too rich. If you don't wash and re-oil the air filter once in a while, you'll have something worse than a clogged air filter on your hands. You'll have a dry, disintegrating air filter. The little foam pieces can go down the intake and get into your carbs, and then guess what you get to clean?
To remove the stock air filter for cleaning, you'll need to at least lift up the back end of the gas tank, which involves unscrewing the tank from the fairing, and unscrewing the bracket at the back of the tank. Don't mix up these bolts, or you could damage your tank when you put it all back together, and that's a many-hundred-dollar part to fix or replace. Once the tank is lifted, pull the top off the airbox (that box with two holes in the top under the back end of the tank), unclip the retaining frame holding the filter in place, and lift out the filter element.
There are three goals to cleaning the air filter:
Any household detergent will get out the oil and dirt (which is usually adhering to the oil). Hand dish washing soap is effective, and safe to handle. You can apply the soap directly to the filter with some water and squish it around, or make up a mixture in a pan and wash it in the pan. Wash and rinse like this repeatedly until the rinse water runs clear. When you rinse, make sure you're rinsing from the inside of the filter to the outside. This will allow trapped dirt to escape much more easily, since most of it will be embedded on the outside surface. If you run water through it from the outside to the inside, you could embed the dirt further in the filter, making it less efficient.
This method gradually washes out both the old oil and the dirt. If you're uncertain whether it's done or not, keep going: there's no way to make the filter too clean, but be careful not to damage the foam.
Once the filter is clean, dry it out by shaking, by hairdryer, with compressed air, or by leaving it to sit overnight if you're patient. The filter doesn't need to be absolutely dry, but the drier the better.
What kind of oil?
Once the filter is clean and dry it must be re-oiled. Walk into your favorite shop and you'll surely find any number of products marketed as "air filter oil". Any of these will work just fine. K&N makes a good foam filter oil. K&N also offer a "kit", which seems to be a poor investment -- all you really need is the oil, and their soap is no better or worse than the stuff you wash your dishes with. Also recommended is Belray Foam Filter Oil spray (also comes in liquid). It's bright blue and very sticky; it should do a good job of trapping your dirt.
After all that, a lot of people do what the owner's manual says:
Any unused engine oil you have sitting on the shelf will do the job just fine.
One thing to note: If you have an aftermarket air filter, use the oil specifically designed for that filter.
Oiling the filter
Coat the filter with a reasonable amount of oil, then squish the oil into the filter. It shouldn't be dripping with oil, but it should be pretty well saturated. One tip you might try: If you have the kind of oil that comes in a bottle, pour some in a plastic bag with the filter and squish it around.
Make sure you replace the filter with the outside surface facing out, so as to avoid drawing any dirt still in the filter into the engine.
If the filter appears to be damaged in any way, specifically rips, abrasion or thin spots, replace it. New filter elements are under $10 from Ron Ayers or your local dealership, and it's not worth the potential damage to your engine just to save a few dollars.
The process, in pictures
First, you must remove the bracket that holds the rear of the fuel tank up. In this picture, the tank was already removed for a valve adjustment. You don't have to remove the tank, just the bracket. Remove the bolts as shown, then slide the bracket rearward. The tank will stay in place.
Next, remove the rubber strap that holds the air filter cover/battery in place.
The clip hooks onto a tab molded onto the inner fender.
Swing the strap off to the side, and then you can lift the filter lid off the air box.
Once you remove the lid, you will see a white plastic retainer that holds the filter element in place. This CAN'T be removed from the airbox. Just push it to the rear and remove the element, being careful not to rip the foam.
After removing the foam element, carefully check the screen in the front of the air box for any damage or debris. It's also a good time to wipe up any excess oil that may be present in the bottom of the air box.
Here's a picture of the "dirty" filter element. It looks fairly clean in this picture, but it's going to get cleaned, anyway.
Clean the element with hot water and dish detergent, until the water you squeeze out is clear. After squeezing all the water out, let the element dry.
Before you can re-install the element, you must soak it with oil. This one got some CLEAN 10w40 oil left over from a previous oil change.
Pour the oil on the filter, making sure you saturate the whole filter.
You must squeeze out the excess oil before re-installing it. Use a drain pan, or similar, and let the oil drip into it. You will squeeze out almost all of the oil you poured onto the element. This can get messy, so wear disposable gloves for this part of the process.
Carefully install the filter back into the airbox, making sure it seats squarely against the screen in the front.
Push the white plastic retainer forward against the filter. It may not stay tight against the filter, but don't worry, this long tab on the lid keeps the element and retainer in place once installed.
Once the lid is installed, make sure this arrow points toward the front of the bike. This ensures that the lid is on correctly.
Replace the air filter/battery strap, making sure the clip is engaged on the tab. It should look like this when correctly installed.
Replace any other brackets and/or body work previously removed. Take it for a test ride and check your idle speed. It should be 1200-1400 rpm. If your filter was severely clogged, you may need to adjust your idle speed.
That's all there is to it. It's a very easy process, and your bike will run better.