In my experience after putting aftermarket reeds on, like the dual layer cf/acrylic it seemed to make my 250R run rich. If you have the airbox lid off and aftermarket exhaust I'd start off with the air screw 1.5 turns out, 30 pilot, needle on 3rd clip and a 250 main jet.
Not sure what kind of carb you are running or what elevation you are at. I'd try and jet it on a 65 degree day, this way if you are riding in the upper 40's or lower 80's you should be good for temp fluctuations.
If it's too rich down low, put the air screw 1.75 turn out. If it's too rich in the middle put the needle on the 2nd clip. If it's too rich up top drop to a 240, 230 or even a 220 main.
If it's too lean down low, put the air screw 1.25 turns out. If it's too lean in the middle put the needle on the 4th clip. If it's too lean up top go up to a 260, 270 or 280 main.
I always ran AmSoil full synthetic 2 stroke oil at a 35:1 ratio.