air filter question

[redbull420]

today i was cleaning my k&n air filter i noticed i had a burnt mark on the filter and i was wondering if any could tell me why this happened .. thanks alot and like always any advise would help
me alot

[trx400Rider]

Never heard of a burn mark on the air filter.
Are you sure its not just oil?

[thebig450es]

Sounds like oil, or you are backfiring really bad

[MtnEX]

Backfire through the carb... generally caused by a lean condition.

You almost burnt her down... better pull your spark plug and second guess your jetting.

Sounds like you are a lucky devil.