Towards the bottom of the Mikuni 34mm carbs that come stock on the Scrambler 400's there is a vent hose with a check valve on it that is routed towards the bottom of the quad. What is this hose for? I think it is to help prevent flooding but I am not sure. I would like to run of all my vent hoses upwards but thought this one needs gravity to help it.

 

its an overflow for the carb and the check valve lets the gas out and also keeps water out

 

Trailbreaker is right on the money. Be sure to leave the hose down. With the check valve, nothing gets in anyway.