Motorcycle Questions? Ask a Mechanic.
There are several potential issues. The most common is a leak in one of the internal fuel tank lines. Possible areas of concern are the fuel pressure regulator, fuel filter, and the injectors themselves.
One other area of concern (and probably the first check I'd make) is not fuel related at all but is the idle air control solenoid (IAC). I provides 100% of idle (zero throttle) air. It is a stepper motor and if it doesn't open to the correct step there is no air available for combustion. The quick and easy test of this is to just crack the throttle (do not add fuel as you have been) to allow a little air to pass by the throttle plate and see if the bike starts. If it does then you know the IAC is the issue. It is a pretty simple change but you do have to lift or remove the fuel tank to access it. If this doesn't cause the bike to start then your issue is most likely fuel related.
The first fuel system check you'll need to do is a fuel pressure check. There are 3 pressures you need to know; the pressure when the system initially pressurizes, the pressure while running and revving, and the pressure when shut down. The pressure gauge gets connected inline between the tank and your fuel line.
Depending on the results of this check there may be other issues to check. You may need a noid light to check the fuel injector pulse signal as well.
I hope this helps. Please let me know if I can be of further assistance. Thanks, P.J.