For about a year or so I have had this carbon stuff in the airbox (black, when thick kinda guey stuff) It doesn't come from the carb cause the inside of the tube leading from the carb to airfilter is clean of this stuff. But that black carbon lookin stuff is all on the walls of the airbox and on My K&N. Its not my K&N i know cause it did this on my paper filters too. I can't figure this out!! Thanks for any replys.

 

what model is it?
I have a 99 scrambler 400 with same problem, its caused by the belt housing exhaust. The belt dust leaves the exhaust tube and is sucked in through the airbox intake leaving the deposits on the filter. I don't know whether this is normal or not though.

 

The stuff in your air box is from the drive blet housing , BUY A GOOD QUALTY BELT, a good Dayco Max, or GoodYear belt will produce less dust and last twice as long as the stock one, but check and make sure the belt is not rubbing on the inside of the housing. You dont want it wearin'through,if you ride hard or alot you should change the belt more ofter cause they do stretch and can rub on the housing,and all that dust aint to good for your clutch either...... hardlydangerous1@yahoo.com