If the low end is set right, it will need to be warm before it will transition (like others have said). That popping could be a rich low end. If it's 4 cycling that would explain it. Lean the low end while the engine is warm until it bogs or hesitates (too lean). Then richen it up from there. I think many of the DA 50 problems is a rich low end, especially if the factory settings are used. Check all throttle positions between idle and 3/4 to make sure it's 2 cycling.