The replacement of the air filter on a newer K-bike, can be a daunting task. BMW has chosen to access the filter element directly under the fuel tank, with absolutely no other way to get to it.
On the K12RS, (like my 98) you can do the work yourself. All the tools needed are in the tool kit that came with the bike.
The first thing you need to do, is remove the seat. If youve never done this, you use the ignition key to unlock the seat. The lock is located on the left side, toward the rear of the bike. Turn the key, push in the lock, and pull the seat toward the rear and up.
Both side skins need to be removed. These are fastened with allen headed screws only, so one small wrench is all you need. The screws are different lengths, so try not to mix them up. There is one screw in the left skin(clutch lever side) that is not easy to find, and is unique to that side. It is up front, above and behind the tire. There is an air duct located right above it. All the screws are around the perimeter of the skin, so you dont need to worry about any hidden screws in the middle.
After you have removed all the screws, check to see whether you have the skin loose by trying to move it up and forward. The skin is very thin and care must be taken to not break the tabs that lock it in at the top of the fuel tank. The lower rear part of the skin must be carefully pulled away from the frame, to allow the upper part to release from the tank. Remember, BE GENTLE !!! They will come loose, and are very light in weight, so this is a one person job.
After both sides have been removed, you will have to remove the 4 bolts holding the fuel tank in place. This is a little more difficult, since the 2 bolts up by the steering head have some kind of thread cement (loctite ?) and are hard to remove. The right side access is a little tight, and you will only be able to turn the screw about 1/8 turn each time. I found that the screws, (allen , again) came loose much easier if you use a cheater of some sort. What this amounts to, is either a small boxed (closed) end wrench or a small diameter pipe on the end of the allen wrench. This will give you the needed leverage to loosen the bolts. Simply use a small wrench (10-13mm) that has a box end, which you slip over the long end of the allen wrench. It should be set toward the end of the allen, with the open end of the wrench pointing up. This will give you app. 4-6 more inches of lever to loosen the bolt. You could also use a small diameter tube, or pipe, that would slip over the allen wrench. Dont use a pipe that is of a diameter, that would be too large, and not have the room to move the allen wrench.
The other 2 bolts are located at the rear of the tank, near where the seat was located. These bolts are much easier to get at, and dont have loctite on the threads.
When you remove the bolts, take care to get the washers and spacers that are under the bolts. The bolts are going through rubber grommets, and there is a spacer in, and a special washer behind, this grommet.
You will need to slowly lift the tank up, and to the right side. This is where you can loose the washers behind the grommets. I would use a piece of tape to hold them in place. You can remove it when reinstalling the tank.
The tank does not need to come off the bike, only moved to the side. All the fuel lines should be left intact, but I would recommend running your tank low before doing this job.
The tank will sit off to the right side on its own, but a small piece of 2x4 will help keep it away so you can get at the filter. The filter is located under a panel that is secured with 4 screws. This is right under where the tank was mounted, on the left of center. Remove the screws, take the cover off, and lift the filter out. You may have to use a pliers to grab the filter, but it lifts out pretty easy.
When reinstalling the tank, take care that all the spacers and washers are in place. The tank has a lot of movement, so dont tighten any bolts until all 4 have been started. You may need to move the tank around a bit, to align all the holes, but it is no problem. I put a little blue loctite on the 2 front bolts, but I thing just tightening them well, is sufficient. Loctite is available at most automotive parts suppliers.
When installing the skins, be careful and always come in from the top. The tabs must go into the slots of the tank, but you will need to make sure the front is also moving into place. I found that sometimes they just fall into place, other times you need to take it off and try again. Dont worry, the skins are flexible, and will give a little. As in the tank, dont tighten any screws until all have been started. This is the time you will find out whether the fit is correct. Again, dont worry, they are flexible and can be moved small amount. The real concern is paint chipping, which I have never had happen. Just take your time, and be careful. Dont overtighten the skin screws. They dont need to be any tighter than the pressure from the small allen wrench. DONT add a cheater !!!
As an aside, this is a good time to change the oil, since there are only a few more allen screws to remove to get to the filter plate.
The total time on this job should be about 11/2 2 hours.