Sounds like you are leaning out due to an air leak. Something like this makes me think you might have an air leak in the fuel pickup line in the tank.
Try this: Fill the tank and start her up normally. She should be a little rich. Run her for a minute then drain the tank till you only have about 1/4 tank of fuel. Restart her and if it's running real lean that is most likely your problem.
If this isn't the issue get back with us. SOMETHING is leaning you out. You try to richen to compensate then when you go to restart you are too rich. Make sense?
If you cooling head isnt on tight or your pipe or your carb..its not gonna tune.
also check your fuel lines..
this might be non-useful information but I figured I would let you know.
my 2.5 wouldn't tune and it wasn't sealing right around the carb..I tightened it down and it tuned right up.
i know its not that cause it ran yesterday. I'm gonna let the tech at my lhs tune/diagnose the problem. if its a major problem I'm just gonna buy a 3.3