So, I am tearing down my new-to-me 03 KDX 220 tonight to replace the spring on the shock and adjust the shims and forks. I took out the airbox, shook out a bunch of cat food (rodents love to stash), and found this giant hole in the side. BTW - There was no lid on the airbox.
Is this a known mod? It makes me nervous to think about crud coming in the side of the airbox.
While I have her apart, I heated and straightened the rear frame:
We used to do that to out bikes in the early 80's when I was on 80s - ha! I've seen a few people do it and have also seen plugs (about 1" in diameter) that come with little filters inside. However, that's an impressive hole and not something I would do on a woods bike. One option is to cut a price of plastic, place it on the inside and then rivet it in place. Prior to riveting I would put sealant around the inside edges.
My son's CRF had the smaller holes drilled into the side. Made a nice entry point for sand and water when he crossed a creek with, well, let's just say some difficulty. It's a wonder none if it made its way to the engine!
I have two holes on either side of the airbox with riveted in dial plates that can be opened or closed. Pretty sure it's factory kx. you might be able to use these to plug that hole.
FWIW, I leave mine open all the time for the intake sounds :) I DO get stuff in my airbox from time to time, but not like above. I have stopped and closed my airbox up on a couple of occasions. They are located on each side of the box.
I don't know how I missed it, but there WAS another hole on the other side of the airbox. It was a little smaller than the other side. Either way, I decided to close both of the holes. I'll be interested to see if I notice any performance changes... I'm doubting it.
It didn't have a lid when I bought it. From the sounds of things, most people decide not to run the lid... I may snag one on ebay and see if I notice any further changes.