Honda Bali sleeve left

Servus, I’m just about to “revise” my Honda Bali because there were some things that had to be done simply, I’m also so satisfied and only have a little problem, maybe one of you has the saving notice After I disassembled the scooter I had a part left, it’s a sleeve, I hang 3 pictures on which you can see the well, my problem is I don’t know where this sleeve came from, which was suddenly under the rear tire… comes in the carburetor almost in the air channel over the needle coming from above from the gas train, but does that really make sense? Vll has one of you nen tip… thank you already Stefan