Hello does anyone know if the water drain tube that is attached to the bottom of your plastic airbox is supposed to remain plugged (closed off) when you are riding? Or are they supposed to remain open, so if water gets in the airbox it can drain right out? Sounds like a wierd question I know, but I bought the quad without the airbox and I just got the box so I dont know whats what. Its a 92 suzuki quadrunner.

It is supposed to be closed. If you get water in your airbox, then you drain it by removing the plug. If you do not replace it, sand, dust, dirt, etc.. can get into your airbox.