At approximately 8200 miles I started hearing a noise which I thought was coming from the lower end in the motor. After careful diagnosis with a stethoscope, it was coming from the top end of the back cylinder. I had a 3 year Kawasaki warranty still in effect so I brought the bike back to where I purchased it from. They listened and also decided the noise was from the top end. I left the bike there for further diagnosis and the next day the Kawasaki area rep stopped in, unexpectedly, and he also agreed it was a noise that was coming from the top end. He provided a Log# for the bike, so if the work couldn't be performed within the warranty time period, it would still be covered. The dealer was too busy to do the repair right away so I had to come back 3 weeks later. I did and after getting the engine pulled from the bike, the technician found the rear cyclinder cam shaft was worn down approximately .030. The hard coating was gone and the rocker arm was also worn. He checked the front cylinder cam and it was also worn to the point Kawasaki agreed to replace the 2 cams and all of the rocker arms. The engine , except for the break-in oil change at 600 miles, has never seen 1500 miles between oil changes. I know that is a real over kill, but that's what I want to do to keep my equipment in perfect shape. I changed to fuill synthetic after the break in change.