3/32" and 1/8" ID is pretty much standard with nothing larger required for even the larger engines. Some companies refer to the first size as med. and the second as large. Buy whichever one fits your fuel fittings the best. Be sure all fittings are barbed and use a positive means of retaining the line on the fitting such as a small clamp, lightly twisted wire or small nylon ty-wrap behind the barb.

Thanks guys! The lack of info in the engine's manual made me wonder if it mattered. Mind you the manual is not terribly informative to begin with. By comparison I was reading through the manual for a Saito gas engine, and it is full of useful info!

I'd read about using barbs and clips or zip ties. With all the potential for vibration it makes good sense!

Gas tends to swell some fuel lines making them a bit loose on fittings. The clamps and barbs insure the line stays where you want it and remains leak free.