Hi Pipes
I live in floody Lincolnshire, but welcome to the forum and to the glories of owning a CB750.
Top end rattle from a bike this age is normal, the cam chain tensioner is not automatic, but simple to set.
Clutch rattle, again normal, some say it goes it you change to a clutch off the F2, I tried this and it did improve a bit.
Front end, you could just transplant a GL1000, that's what I'm looking for, it has the dual disc arrangment, and should just bolt on (Someone tell me if I'm wrong). :blink:
Rear springs, may just be set too soft, or lost all their fluid, an after market set is not that expensive and can be bought new.
Horn, thats probably dirt in the switch contacts, a spray of good contact cleaner, like WD40 should clear it, if you decide to dismantle the switch, watch out for the tiny spring(s).
Parts are freely available for the CB750, and most engine parts work across the most models. Just remember that there is also a DOHC CB750 and not all ebayers state this.Do your research and if in doubt ask.
That all said, welcome, remember, when things don't go your way, to chant the mantra \"it's only a hobby, it's only a hobby\" :lol: