stock 400ex riding without the air box lid.. how woud u find out if u got dirt inside ur engine or carb.. i am putin my air lid back on because i am worried about dirt and dust getin inside my engine.. but wut are the signs if that does happen

 

Look in the box see any dirt?

Hopefully the filter did its job then. Only thing you have to worry about is water.

 

look in the tube that runs from the filter to the carb if their is dirt in their then your filter is passing some small particles. i prefer a foam filter myself. they may not flow as good as paper or guaze but i think they catch more junk. i have a k&n on the jeep and my intake tube alwasy has dust in it which means the filter is letting stuff pass