Are you running a Mikuni TM28 carb? If so, what are the pilot jet and main jet size? Are you running an airbox or a K&N style air filter?
As far as fuel mixture, I run 6 OZ Motul 800 2T synthetic oil per gallon of 110 leaded fuel.
The only time I had a problem with a bog out of a corner was during break-in of a big bore kit that the guy told to go massively rich from the settings I was accustomed to. I figured too rich , no problem, can always lean it out after break-in!