81 z750ltd rattles when on sidestand

hi i am a new member but i am quite well versed in motorcycle repairs ,however this has me foxed .the bike a 81 750 ltd four cylinder ,runs great .leave it running on the side stand & a weird rattle ,sounds like a very loose chain flailing about .noise comes from the left hand lower engine area .
i have done the following to try to cure it .
1/ replace starter clutch & cush drive .
2/ clean carbs & balance .
3/check valve clearance all ok
4/overide automatic cam chain tensioner ,cam chain tight not that rattling.
i have considered the primary chain however it was within spec & any tighter it would be virtually imposible to install the jackshaft assembly .
the bike pulls strongly ,idles smoothly ,& is silent when vertical ,rattles when leaning to the left & has slight rattle when leaning to he right .
the only other fault is that second gear is slightly noisey when cold.
i have been out on the bike & given it some stick to see if the noise increased or something went bang ,stayed the same .
the bike has done 56000 miles but is very tidy .
when i removed the sump to change the starter clutch it was clean as a whistle inside no sludge etc .
the jobs i have done have helped slightly but the noise is still there .any ideas or should i leave it to develop.

I'd put the bike on the center stand and if possible lean it to the right(this will minimize the oil loss).Remove the alternator cover(have a new gasket on hand as the old one usually tears) and check the stator for tight fasteners,and the rotor for loose magnets.

The over running clutch for the starter system I believe is behind the rotor, so check it for loose parts too.

thanks for the info,i never thought of loose rotor magnets.so i will check out asap,the 650 & 750s have the starter clutch mounted on a jackshaft driven by a hivo chain .i have already been into that can of worms with no improvement .

i have checked my rotor magnets all ok.
i am reconsidering a cam chain problem .the auto adjuster is only going out around half way .the chain is tight when i test staticly with the cam cover off .i added some packing to increase the spring pressure on the wedge that tensions the chain .
however when the tensioner was out when i pressed on the tensioner blade it moved out seemed to be pressing on the chain then seemed to press out a bit more ,i think the chain was seating in the groove that wears in the blades & tensioners etc.
i have a spare tensioner & i am going to drill & tap the 17 mm headed cap ,fit a bolt & locknut to make a tightwad manual tensioner ,what do you reckon

I would never leave the bike running while on the side stand. Always afraid of oil moving to the left and the right side not getting enough.

On the centre stand the primary chain can make quite a racket if the carbs are out of balance.... but you did mention that you had balanced carbs so doubtful thats the cause.

Loose cam chain is usually audible at most speeds .. easiest to hear at mid to low speeds. Cant think it would be any worse on the sidestand but then again I try not to leave engine running while bike is on sidestand.

I'd also suggest looking at the clutch basket,and the clutch disk's for wear/looseness.

i just got off the phone with our resident head flower and he said to check your ring gap.

thanks for all the input ,the weird thing is sometimes the bike is quiet as a mouse then all of a sudden all hell brakes loose ,if you blip the throttle it shuts up again ,almost like a hydraulic cam follower on a car .oil pressure is good .
i am going to make a manual cam tensioner from a spare one i have ,then i know if its the cam tensioner backing off .