First to answer before someone asks why I would ever want to remove the air box. I mounted the cbr motor on a gokart frame and regardless of how the engine sets the air box is somehow in the way.

what would happen if I ran the engine without the airbox? I had it off for a while (not running) and just screwed the Intake towers (circular tubes inside the air box) straight into the manifold and it looked and fit perfect but there were a few holes I noticed on the intake manifold that get connected / blocked when the air box is attached....so Do i need it on for the engine to run properly? can i just cut the airbox and use the bottom to block the holes?

 

i used to race karts on the dirt a trick we used to use is find one large foam dirt bike filter or 2 or 4 smaller ones. oil them place them over the intake tubes and clamp or zip tie them in place. it`ll keep all the **** out and should give similar intake flow flow remember in the bike it`s getting forced fed air from the intake runners on a go kart it wouldn`t be getting the air jammed down its throat it`ll only suck in what it needs.

 

And of course now you have to filter each velocity stack (x4) instead of one filter. But I've seen it done on lots of engines.