The YS uses a sealed system. There are no "loose lines" from the tank. The best plumbing you can use is T fittings/fuel dots installed between the tank and the fuel filter on the incoming side and between the tank and the check valve on the pressure side. You only need 2 lines to operate this engine, one for the pressure one for incoming fuel. Uncap them both and fill through the fuel line. Use the pressure line for the overflow.
DO NOT use a fueling valve as they are prone to leaks.
You need not prime the engine through the carb. Simply open the throttle to full and hit it with a starter for 5 to 10 seconds. This will pressure up the tank and give the engine enough to fire. Reduce the throttle to a few clicks above idle, connect the starting battery and light it up. Allow it to run for 30 seconds at fast idle then set the needles.
Go to the instructions at
www.ysperformance.com and follow them for your setup.
Good Luck!