In the olden days before risk assessments and the need to have blame for every little act of misfortune we used to mix and match with out much care and (it was pre internet) we used to take what was available at the time.. These days insurance companies will screw you if you so much as fart without thier written permission.
So will the bike be any worse for it ? maybe and maybe not but will your insurance company have a kind eye if it goes arye ? probably not. Ps my old 660z was a little twitchy on 1/2 worn siracs but it was probably more due to the squared off rear rather than the front as it was the same on T63s allround.

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ex XT660X Tenere, now XT1200Z Super Tenere