I was very disappointed today when I went to change the air filter on my brand new (7 hours old) 2012 crf250r today only to find a great deal of Sand and grit behind the filter and down into the fuel injection inlet. There is also foreign oil (engine oil I expect in the air filter). I have been changing the filter after every ride and on the last change I overruled it a little bit.
However it looks like the cause of this problem may have been factory related as I was removing the air box I found the clamp that connects to the fuel injection was quite loose and there is a lot of dirt between the airboot lip and injection inlet.
So now I imagine my engine is dusted and the oil in the filter is blowby so ill be up for rings valves and either a home or a barrel on a brand new bike.. Great!

Cheers
Alex