Ive been looking at an 81 550 with 26000 miles on it the guy wants $600. There is a small knock when the engine is running cold, it goes away when it gets warmed up. The guy selling the bike says it did it when he bought it 7000 miles ago, he brought it to Kawasaki and they said it was a little piston slap and it was common with those bikes and nothing to worry about. Any body else run into a deal like this? Let me know please!