As I understand it the vent lines running from the carb allow the bowl to maintain atmospheric preasure to maintain proper fuel levels in the bowl.

If that is correct there is air flow into the float bowl through these vents.

Shouldn't they have some sort of filter on them?

Do they have to hang down under the bike?

I've seen some people put "T" or "Y" connectors in their lines just below the carb. This is supposed to maintain proper preasure bowl even if the lines hanging down below the bike encounter water or other airway obstruction. If a "T" or "Y" can be installed up high, why can't the hose just BE up high?

 

The only Issue I might see is if the float sticks and gas comes out of the line. the last place you want it landing is on a hot engine or the exhaust.

 

correct, they are air vents AND overflow drain hoses too.

 

So the "Y" connectors make sense. What about filters?

 

I put a T in mine and ran the one hose down to the littel hose holder down low. No problems. Not sure why there are two vent hoses.