What is the use of Yamaha motorcycle double throttle line?

The double throttle line can make the throttle be pulled by the throttle line when refueling and receiving oil, instead of being pulled by the throttle line when the single throttle line only has the throttle. When receiving oil, it will automatically rebound by the spring force of carburetor or throttle valve, which can prevent the throttle valve from returning in time for other reasons. But in practical use, it is not necessary for this kind of small displacement vehicle, and it is no different from the ordinary single throttle line.