Gemini 80 carb
Find out who made the 80 cc motor and try to get a manual and you may find what parts it shares with other bikes. It might be a Fuji motor which is a predecessor or is similar or even related to the Hodaka Ace 90 and Ace 100 motors which use mikuni VM 20 mm and Vm 22 mm carbs. Also, the Rupp L 100 used a mikuni 20 or 22mm carb like the one used on the Hodakas. Another similar bike, the Chaparral used I think a Fuji motor where I think they put their own names on the motors, but the parts may be the same as the Fuji or Hodaka.