I have an open hole on the top of the motor. Check out the pict:
http://www.motoxpress.com/300ex/mystery_hole1.jpg

What is it?

MX

 

Is the hole threaded? My Warrior has a bolt in the head to verify that you are getting oil pressure. May be what that is for. Have you been running it like that?

 

I looked at my 300,

it is like a blow off valve(like on a car)

from what i seen a hose comes off there and goes through
a tube and then into the intake(next to the airbox).

 

So it must be your crankcase breather. Route the hose into the airbox or put a breather on it.

 

yeah the hose ran into a little clear box
than into the intake

 

Yep, it runs all the way though your valve cover through your cylinder and into your crank. It's just a breather in case your crank creates too much pressure. If you dont have it you could be going through gaskets pretty quick. It's an L shaped type of deal. On the 250X's the open end faces the front of the quad and a tube runs from it into the frame. The tube might be on the frame on the EX's but I dont know. Otherwise just run it to your air box.

 

on the 300ex,

it bends to the back of the quad.