Does it idle real high after a high speed run then eventually idle down?
That could be a lean high speed,

How much space is there between the slide and the inside of the carb? should be about the width of a credit card or so.

If thats set right, its gotta be your tune,

You could have used the low speed needle at one point to compensate for an incorrect idle? or vice versa.

Id check the gap,

Then reset my needles and tune the high speed then the low speed.