81 gs 450L build question

[hellize]

Hello,

I am thinkering on my gs and I have a question, maybe you guys can answer it.
So I want to put some conical air filters on to save some space, because the stock airbox is HUGE and there is a rubber hose connecting the a hole on the top of the engine with the airbox. If I put the cones on, there will be no place for the hose to connect.
Now I don't have a clue what to do with the hole on the engine?! What is that hole for?

My engine is identical with this one, you can clearly see the hose connected to the engines top:

http://advrider.com/forums/showthread.php?t=709663&page=3

 

[Saberball]

That is your crankcase breather vent tube. When the engine warms up, any moisture in the oil should get heated up and evaporate and move it self out of the crankcase through that breather tube. The reason the tube connects back to your airbox is because of the EPA not wanting crankcase vapors released into the atmosphere. In theory they get sucked back through the intake and burned up no problem. Before the EPA cracked down on crankcase vapors being released into the atmosphere, the vent tubes were longer open end tubes that routed down through the frame in a way they would just drip accumulated moisture on the ground.