Paul,
After reading some more of this, especially the part about the "it fires and runs then dies" part. I think your sensor needs to be retarded some. You can't hurt anything on a DA by moving it...not even by moving it from as far as it will go in both directions. What I would do is move it back about halfway from where it is sitting now. Do mark where the edge of it is so that you can put it back exactly should this not work out. I did this on my 100 and it made some difference in the way it started. I bet you have a prop that is a pretty high load on there don't you? Also I noticed that you are getting ready to switch over to full synthetic...be sure to follow that DA manual to the letter on the breakin, and the part about the oil after breakin. I would still give Dave J. a call about the engine. You really need to get answers about this from 'the horses mouth' so to speak. It is very unusual for a DA not to start rich...very very unusual. The one thing I don't know much about on that engine is that rear induction as that is the first engine that DA has put out that has that. You really need to make sure there isn't something going on that could do damage to the engine. It could be something wrong with the carb or something back on there on the induction. If the engine is flooding like you suspect you could do damage to the rods. The guys here are real good at finding things, but THE man to talk to is Dave about his engines. Brian can help you too if Dave is not in. These engines are works of art, and I would hate for anything to happen to even one of them. It is rare for anything to go wrong with them as they check those things very good, but some things are hidden until it's ran for awhile, or it could've simply developed a problem. Those guys are very good at what they do, and I gaurantee you they can help you. They are very thorough over the phone to make sure they give complete advice on things. Try the above and give them a call.