What kind of motorcycles are allowed on motorways/freeways?
What engine size motorbike is allowed on motorways/freeways?
What is the lower limit for engine size on motorbikes for using motorways/freeways?
「高速道路」= motorway (イギリスの言い方)かfreeway(アメリカの言い方)
「何CCから高速乗れる?」= What kind of motorcycles are allowed on motorways/freeways?
他の言い方も使えます:
What engine size motorbike is allowed on motorways/freeways?
What is the lower limit for engine size on motorbikes for using motorways/freeways?