How do I set my KX 250 idle?

Its a 2000 kx 250 2 stroke dirtbike and it runs fine except for it doesnt idle in first gear unless u keep giving it ga. if u dont it just stalls. as in, in neutral...i kick...its on....it can idle in neutral....then i have to give a little bit of gas and click it into 1st or else it will just stall....BASE line...i cant idle in 1st gear with out givingg it short bursts of gas and keep the rpms up...but not too too high. how do i set the idle???