Fuel flows out a rubber black hose when running

Sounds like a leaking fuel hose, I would replace it. Does it have clamps there it attaches to the carb and fuel tank?

"Hoses tent to break due to vibration and ageing, if you can see it, it would be easy to replace, you don’t specify exact model, but Yamaha usually has special hoses you have to replace with (90 degree, or specific distances), buying an exact replacement is the easiest way of replacing, but a normal hose cut to the distance could be used too if it is not so bent that blocks the fuel flow... Up to you to decide, they used to be cheap at Yamaha…

Also hoses tent to have pressure clips on each side, please confirm the fuel comes from a broken hose, and not from a missing clip on one of the sides."