I have a DA85 on a 100cc Yak and it runs great but the mid-range or half throttle it breaks up pretty bad,can that be adjusted out without messing up the high end?

what prop and exhaust r u running?

24x12 3 blade and stock pitts

its known as the DA burble. Get used to it for about seven gallons of fuel then it should lighten up

restrain the plane, turn it on and set go to1/4 throttle or the point that burbles, and lean the low end while its running it should go away..... i bet your throttle response will improve too