I've had to this when my z was down for months. I drained it VIA 12mm bolt under the gas tank there is two and very accessible. I had a siphon hand pump and spent 30 minutes and only drained a gallon. Be careful to I did burn my hand a few times removing the bolt before I decided to wrap my hand in a tshirt. I've heard of another method that involves disconnecting the line leaving the filter to the fuel rail and having the pump running.