Codfish,
I have just packed them up and included a copy of the purchase and a detailed letter about the problem. When I have had muffler problems I also include photos of the problem. As I said, all eight times they have replaced the bearings. Twice they have replaced the cylinder head when their muffler manifold stripped the threads. This time they also replaced the crankcase.
I guess I'm just lucky or the documentation helps?????

I now have an OS 91 FS on the AT-6. We'll see how that works. I do like the sound. We have a number of guys here with older OS 4-strokes and they always had tuning problems, numerous dead-sticks, andwasloose muffler issues. That's why I chose Saito 4 years ago. Now I understand the newer OS 4-strokes are better. So I decided to try one on the AT-6. The fact that it was a $100.00 less than the Saito with the Tower promotions made it a no brainer!