Just bought my vfr 400 and was emptying the fuel tank before removal and came across an additional valve on the outlet of the fuel tap. I believe past owner had issue with fuel tap diaphragm and instead of fixing fuel tap installed this valve?? As soon as I opened valve fuel overflowed from carbs. Has anyone seen this before and can shed some light on what he was thinking or if I have missed the point completely.

Total newb so not sure how to attach photos

Could be that he modified the fuel tap so that it flows all the time and he added the valve to shut it off??