Wow Yamahas are super reliable. I don't know how you could have 8 bad valves and a bad chain and not have a bike that rode like shit. That's very weird. I'd get another motor. Actually I don't know what I'd do b/c I wouldn't be able to afford either. I could spend my money elsewhere. Man sorry to hear that. I don't want to knock your mechanic but that's just kinda crazy!!