Motorcycle Repair: Air Box and Idle Problem, 1981 yamaha xs650, air leaks

Question
I have a 1981 Yamaha XS650 Special that I've been rebuilding. I've noticed that there are two hoses that run out of the bottom of the air box throat, where the air filter housing connects to the carbuerator intake. The tubes combine into a T between the two halves of the airbox and go up and daylight under the seat. However, the daylighted end has a clamp on it, indicating to me that it should be connected to something, but I can't figure out what. Where does it go?

This leads to the real problem. When the bike runs, sometimes the idle is really low and it dies, so I adjust the idle screw and then, as a result, sometimes the idle is really high. I can't get the idle to stay constant. I just rebuilt the carbs, thinking that was the problem. Could that unhooked hose end be the problem? If not, how should I go about tuning this up?

Thanks.
Jeremiah

Answer
Jeremiah,
that tube is for the engine breather.
It hooks onto the top of the engine
at the rear center of the head.
It may affect the way it runs a bit.

-Also check for air leaks around the carb
intake tubes and make sure the rubber caps
are on there too. Any air leaks will affect
the idle badly.
-Were the idle jets cleaned well?
-Is the compression good, valve clearance checked?
-The carbs may need to be synchronized
with a mercury type gauge to get their
idles set evenly.