Well first the good news, it actually started!
Prelude: Bike was totalled by previous owner, bought it to rebuild. First time attempting to start it coolant and oil mixed, turned out heads were split open. Put in replacement head from a 2001 F4i after adapting it for the F4. New headgasket, checked valve clearances, checked cam timing, reinstalled everything. Fresh oil, fresh coolant,fresh gas.

Here's what happened. I hooked up the gas tank today, triple checked fluids, and decided to give it a chance at starting. Took forever to start, I assume due to the fuel pump filling the carbs or something. Leading up to that it was making some weird plopping noises, almost like when a hose is under vacuum and you pop it off real quick, like a suction cup or something. It seems directly connected to the ignition because I unplugged the coil wires and the sound completely went away. Once it started it ran really rough making that same plopping noise, just much faster, itidled for a second at 1000rpm, then slowly dropped off until it died. By then my battery was dead from cranking over so much, so I pulled it andplugged it into the charger. I pulled the spark plugs real quick and they've got a lot of gas on them. No gas or oil or anything was coming out the exhaust ports (headers not on the engine) though. So right now I'm tired and stumped.

Why did it take so long to start?
What is that noise and should I be worried?
What's with all the gas on the spark plugs?

Thanks in advance if anyone can shed some light on this!