Tore this thing apart since it would not idle, only runs with choke. Figured the carb is probably gummed you.
noticed this hard plastic hose, not connected. It goes back, under the seat to a canister of some sort behind the shock bolt. It’s down low under the starter, behind the transmission. Is this some sort of vacuum canister for emissions?

 

Hoses got better designed once everyone figured out ethanol petro screwed them up over time. same with the carb bowl floats andd jets.
I change all hose on older scoots, run seafoaam thru the fuel system every 3-6 months.

 

Cleaned the carburetor and it runs like a dream. Just needs more power.

 

FWIW, that's part of the evaporative emissions control system on California bikes. That line goes (or went in your case) to the charcoal canister.

 

It`s a good idea to carry charcoal on the bike, you never know when you may want to stop and cook something on the grill...