I use two different battery testers one is a carbon pile load test and the other is an impedence test battery easly passes both tests. As far as the double oil your right I am now adding straight gas to it and will run it to see if it clears. New plugs are cheap so when I know its back to just gas then they will go in. I still want to know what the O2 numbers should be at idle. I think it is interesting that I have been told in automotive systems for almost thirty years now about the things that will kill an O2 sensor and Yamaha blows all kinds of junk at it and thinks it will live.