Not trying to be argumentative but he said it was fine for a couple of months. and then in stop and go traffic it happened again. I have a hard time buying that for a couple of months the clutch was good and somehow air caused this issue. I know these are hard to deal with . believe me ive had my moments with C14 clutch bleeding. I still say its the slave. Stop and go traffic it was being used a lot and the piston seized then un-seized. Take it apart. I bet 20 bucks its full of crud. 78k miles he said.
Normally I'd agree with you, but on mine one of the earlier steps was to replace the slave cylinder with a billet aftermarket one (
http://www.oberon-performance.co.uk/acatalog/Kawasaki_Clutch_Slave_Cylinders.html)and I still had the problem after I fitted that. My OEM slave wasn't that crudded up either when I took it off.
Regular cleaning of the master cylinder is also needed and I use a piece of very fine stiff wire to clean out the return hole in the master. It's not the best design of clutch master/slave I've seen, and seems to be prone to issues given what I have seen on many of the other Kawasaki forums (it's used on LOTS of Kawasaki's).