Not sure on the Z as i owned an R but condition is a big light as to how the bike was looked after, so check the engine cases for chips, peeling or wearing of the paint and also the rims/spokes.

At that milage the valves would have need to have been checked at least once at 12k miles (if i remember correctly). If not it should cost a couple of hrs labour.

At that milage the chain and sprockets will be pretty much on there way out or done if they havent already been changed. Also check that the cush drive rubbers are not too loose, if there is more than a couple of mm rotational movement on the rear sprocket they probably could do with either changing or packing out.

After these few things from what ive read its pretty much standard looking at a bike and feeling how it rides on a test ride etc

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Plough on