To do your own service, even the basic stuff, the service manual is almost a must to do justice to it. The air filter is under the top shelter (false gas tank). It's big and round. To replace you will have to remove the seat, then the covers just below the speakers, then both radiator shrouds (lower black plastic on sides with fins) and middle cowls (colored plastic panels just above the radiator shrouds), then both storage boxes, then the top shelter. At this point you will see the cover for the airbox but it still has some parts mounted on top of it. You will have to remove those parts and then the cover for the airbox to get to the filter (may be able to avoid totally removing those items but easier if you do). There are a lot of details I left out of that but this is just a basic summary and you'll need the service manual to really get the scoop on those details. As Dexter stated, it will take some time to get there. Not a rush job. Not difficult really, but time consuming. Putting back together is the reverse... being very careful to get all of it back in the right place the right way. I may have missed a bit here since this is all from memory. Oh, and you don't have to remove all the outer plastic panels the manual seems to imply that you do, just the ones I mentioned. I've gone just short of actually removing the airbox cover so check the manual for that part to be sure. I'll be doing this on my CTX1300 very soon.