Faults:

Cam chain tensioner (these things die easily; mine went shortly after I bought it)

Had to replace the cush-drive along with it.

Poorly serviced (fork oil, bearings, brake fluid, master cylinder...)...

...and poorly treated (crash damage, square rear tyre from burnouts) by the previous owner (s).

Watch for chrome pitting around the lower inside of the fork legs.

Bake brake drags very slightly (not sure why yet).

It's spent most of its time in pieces making up for typical servicing requirements.

The previous owner dropped it while 'washing it' and cracked the side cover. I'd suggest some frame sliders to restrict this happening again. Motovationusa.com do some decent ones.

General Comments:

Handles great when the tyres, wheel bearings and cush-drive aren't knackered.

But it could do with braided lines, as the rubber hoses are getting quite spongy at 15-16 years old.

Odd thing about it is that the chain is measured by how close it can get to the swing arm without a rider (or so the manual says).

The ZXR400 is a more responsible step up from a smaller bike in place of a 600+ (believe me I know). But the power out of corners is lacking over 100km/h, so the novelty of owning a 400 wears off pretty quickly.

In comparison to other larger bikes I've ridden, (Aprilia SL1000 Falco, Kawasaki ZR750f) the low seat height and weight makes riding easier; all you have to do is throw your body in one direction and the little Kawasaki actually responds (I'm 65kgs, so it means a lot to me).

Still, the Aprilia out classes it with braking quality (Brembo) and a general feeling of stability and steering responsiveness (Ohlins and it's Italian). Not that it equates to anything greater than the 400 in regard to cornering speed, it just feels easier to ride. Such a pity it's so heavy and large (he says, hoping Cagiva releases a Mito 500 or 650).