I normally clean the air filter every 3-4k kms. I take my car to the bike service center!!!..yes Bike service center here all the spanners are easily available and more importantly they have a small air gun which they use to clean the break dust or clean the bikes air filter. Tap the filter 4-6 times on the floor and then just give it to them and they will clean it thoroughly. It works wonder and the high pressure air gun clean the filter nicely. much much better than vacuum cleaner. Time needed : Just 10 mins.