There was a yank fuelled rumour getting around about 12's having weak clutches. But according to easyrider from
zx12r.org (and i would trust him) it had more to do with ppl doing repeated strip runs without letting the bike cool between. NOTHING will stand up to that, eventually repeated full power launches are going to make it slip.
There was a mod that pumped more oil into the plates (that looked pretty easy from memory) on the site, a search there would find it. There was also a LOT of info on it that all seemed to counter the other (as per the norm there) but the oil mod did seem warranted if you did repeated drag launches. LOT of ppl on there running heavily modded bikes with std clutches but (if you can beleive septics).
I have to admit I dont know about the early ones, but unless you are really hard on it (why?), have a HEAVILY bombed motor or there are reasons to suspect damage (not a design fault) then it is prob in your head. Dont forget the amount of time the clutch is actually in use. once its out it is all locked up and 12's dont really need clutch slip to get em rolling or pop the front up
It doesnt look too hard (I havent done it) to drop the clutch cover off to have a sticky beak anyway. After 6 years the plates very well COULD be worn but not from a design fault IMHO. For piece of mind go for a look, check plates for wear, rivets in the bottom and for scallops up hte basket sides. Go to zx12r.org and search clutch checking, replacement.
And dont try to get a slipper clutch for one, NO ONE makes em, NO ONE.
STC in Italy were not even interested in looking to see how different a ZX10R one was (they DO them) to modify.