Need help with buckin bronco!!!

Hey guys,
I have a 77 kz 1000 that I just freshened up top end, split cases and did inspection, new cam chain etc. The problem seems to be in the clutch. I inspected the clutch during the rebuild. All frictions and steels looked to be in great shape. I picked this motor up from a donar bike, so I didn't ride her prior to tearin her down and doing a total rebuild. I did install a new ape bearing clutch pusher and new stock springs from Z1. I adjusted the clutch as per kawasaki repair manual. I started with the worm gear assembly the clutch pushrod sets in and adjuster till i had tension and backed off half a turn, then moved on to the center section, and finally the clutch handle. The bike runs and shifts great when its cold, after about 45 miles of riding she will buck like a bronco as the clutch is released normally, but still shifts fine and the clutch does disengage the motor as it is supposed to. I have to really slip the clutch to get her not to buck. Can that ape clutch pusher be causing the problem, or are the clutch disks swelling? I rechecked my adjustments and they are spot on with the manual, with about 1/8th freeplay in the clutch handle.