Well I just had to tell this story to you all. My brother-in-law has a 400ex and well his battery needed charged. So we had the back plastic off and I was telling him about my K&N filter and I asked if he had cleaned his yet and he said nope. So I lifted of the lid and what did I find a big wad of cotton and snakeskin!!! Apparently a little rodent had decided to drag enough of this stuff in the airbox to fill the entire thing and make himself a nice little mobile home. He did all of this by carrying all of it through the breather tube under the gas tank. What a mess. Who knows how long he had been working on it and how long its been there. Remember to check your air filter and clean t regularly even if you dont ride in tons of mud or sand!