Hi.
The air cleaner case has 2 ducts coming from or into it one goes to the carb.
The other duct on mine is not connected to anything other than where it comes out of the case. It has an open end about 1 1/2" dia ending under the gas tank with a crankcase breather connected to it.
Where should it connect to ??? (cannot see it in the service or owners manual) nor can I see any suitable connection point.