It would take a lot of typing for me to give you the step by step.It´s easier if you buy the service manual for your S50. That is what I did,it gives the step by step.I think it was at least 60 or maybe 100 dollars but it will answer any question you have. Of course the dealership will claim they don´t know how to change air filters. That is money out of their pocket. But even with a service manual I think I don´t want to change my air filters. I would rather change tires and balance my wheels.( already did it once ) Seriously, I will never buy another S50 as long as I live. In many ones I consider the bike to be the most pain in the neck, aggravating piece of crap to work on I have ever owned. However, I must say the bike has a reputation as a very dependable motor,fun to ride,good gas mileage and looks great. Just a %!¤ to work on. If you want to pay dealer to do everything and you just ride, then it´s a great bike. Want to do most of your own servicing your bike,don´t buy a S50. Think about a Ural sT solo.