Problem with Mighty Demon 750

Yeah, Ive got a 39 as my IAB as per stock spec. So putting a larger one in would lean out the idle circuit?

The stock IAB (outer air bleed) should be .070
The stock MAB (inner air bleed) should be .039

A larger air bleed allows more air in the emulsion tube leaning the air/fuel mix.
I run a .061 IAB BUT I also reduced the IFR from stock .031 to .028 This change in the idle circuit took care of the rich idle and light cruise up to 2500 rpm I had.