I insist on Tygon brand fuel line. The stuff I use is yellow.
It remains flexible and pliable long after any other brands I've ever used. Also with the Yamaha, it doesn't require hose clamps.
I'm pretty sure I'm using 3/16th inch ID Tygon on my bike.. I keep 3/16" and 1/4" stocked in the garage at all times. It stretches over bigger fittings well.
The added benefit is you can see through it to know if your line is plugged up and there's no fuel in it. It costs about twice the price of the black rubber junk sold at car parts stores and you usually have to ask for it by name (and usually the kid working at the store doesn't know what it is.)
They sell it at O'Reilly Auto, Napa, and a local mom and pop shop I do business with.