i have recently picked up a 94 yzf 750 r, im new to sports bikes and not long had full licence.
When i picked it up it needed a couple little bits doing to it which was no problem.
when you turn the ignition on i got a wizzy noise but now suddenly that has stopped happening altogether but bike still seems to run ok. was wandering why this is and what it was and do i need to get a new whatever it is????

if you are referring to the noise you hear when you first turn the key on its the fuel pump, completely normal.

does it make any difference at all that it doesnt do it at all anymore?

this is a noise that happens when the engine is not running correct ?

If so then I would think it is your fuel pump. I remember it being a mechanical noise .

if the noise stops maybe its because the fuel pump only primes or pressurizes the line once on the startup cycle.

there is a common noise on startup of certain bikes it is like I said the fuel pump (and FI system on newer bikes) getting into start up mode.
I just am not sure if your noise is the same

it runs for 5 seconds then stops , then when engine is running , check it by flicking the kill switch it will run each time for 5 secs , its a safety device to switch off in the event of a crash so the pump stops if the engine does ,