I have a YT6800 that I belive has a bad cam or lifter so i want to part it out or sell it whole. It ran great last year but now only runs on one cylindar. many good hard to find parts. Let me know if you need something. I live in Waterford Michigan.
Another thought, typically a cam will not just wear out. You should notice a gradual power loss. It may be a bent lifter rod, or what I'm betting on is a stuck lifter. I had this happen to me, I simply added a couple oz. of Sea Foam to the oil, and it fixed itself in less than a minute. Might be worth a try.