Hi there everyone i'm Steve'O i have a XT660X 2004, how often should i change the air filter?

Official change interval for a stock paper air filter element is 12,000 miles.

It depends very much on your riding conditions though. Even if you're only riding on roads I personally would never leave it that long.

If you're running an oiled cotton gauze element, then clean and re-oil annually as a minimum but again, it depends on riding conditions.

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Thanks Pleiades i bout the bike around 5000 miles back and yes i'm running cotton oiled, how do i clean and what oil do i use to re-oil? Thanks