Before you replace try adjusting the clutch rod play. This is written for the regular KZ750 which had a very similar motor so you may need to improvise. Slacken the clutch cable.
There should be a small cover on the left engine cover, in front of where the sprocket would be if you had x-ray eyes. Remove that cover (two screws) and see a lock nut over a slotted rod. Holding the push rod with a screwdriver, loosen the nut using a ring spanner.
Turn the push rod clockwise until you feel contact then back it off half a turn. Holding the rod in position, tighten the lock nut. Adjust clutch cable and put all the covers back.
If that doesn't work, you need new clutch plates. With your low mileage, just cork ones. Your springs and metal plates should be good, unless they come out "blued".
You may need a gasket or two too.
Go to Motorcyclesuperstore.com , type in the make, year, and model. Find the exploded clutch part page. Order mineral disks, stationary disks, new gaskets, and new spring (& sealer?).
You will have to fabricate some tools to push the basket closed and order some big metric sockets to turn basket loose from the transmission. If the outside basket is worn away in places you will have to order a new outside basket. They may offer a kit...or may not?
When you open it up look over the clutch lever arm for any wear or bending...it will save you replacing the speedometer magnet and pick up if any wear is found, .... any wear or weakness and the new stronger spring will finish off any weakened part. ... when it breaks it will take speedometer magnets and pick up in collateral damage.
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