Something you said got my attention and might be your fault.
From a "off" position, look at the secondary throttles when turn the key to the "on" position. They should flap full open then full closed as a sweep check. Is that the same sound you mention or a different one?
Try starting the bike and giving it the slightest hint of throttle as you do so, the tiiiiniest bit, just enough to crack the throttle blades. If it stays running, you've isolated your problem, it's a bad ISCV stepper, if it stalls right away again ignore the TB assembly and start looking elsewhere (coils, plugs, plug wires, injectors, fuel pump, fuel filter), think that completes the list of candidates lol.
Blessing on your pocket book, hopefully it's a loose wire!!