adam, not sure what you mean by gravity fed bike. From what I got while studying the service manual is, that your FZR does have a fuel pump. So I would start by downloading the service manual [http://www.scribd.com/doc/75458001/1-Yamaha-fzr1000-89-Service-Manual#download|from here.] then start systematically. Start with your fuel tank. Make sure that your cap is vented, make sure all hoses are without cracks and connected. Check the fuel filter, it is possible that it got occluded with gunk when sediments, rust, etc got sucked into the filter. It does start if you use a battery boost, to me that would mean that your battery is going to get run down to. Check the cells to make sure that none of them is shorted. Clean all your electrical connectors. Right now, I would concentrated on fuel delivery. Tank>lines>Pump>Filter>Carbs>Sparkplugs>timing.
Hope this helps, good luck.