When the kz is cold and I. Try to start it, most times but not every time, there is a grinding noise. The noise happens until the bike starts or tries to start.
I think this is an issue with my starter. But I don't know if the state is going bad, if I need to check my battery or what can be done
If the battery is fully charged then grinding noise could br starter motor or could be starter clutch (big job)
My bike used to make an occasional grinding squeal when starting from cold and this became more common over the years. I feared the starter clutch was to blame but decided to investigate the starter motor first.
If you dont have a manual you can download one from the home page here. Go to "Home" and scroll down on the right hand side and select gpz750.
I took the starter motor out - easy job - opened it, cleaned the carbon dust off the commutator ring with contact cleaner, greased the planetary gears and generally gave the unit at good service. Put all back together and end of problem.
Had this not worked then next would have been to tackle the starter clutch. Not an easy job on the 750/4s. There are a few videos on youtube.
Hooefully servicing the starter motor will solve your noise problem also
