If you are running a 45 pilot and a 190 main jet, I assume you have a 1985/1986 model and somewhere above 3750' above sea level elevation.

If this is the case I would drop down to a 42 or 40 pilot and set your air screw for 1-5/8 turns out, then try to set your idle.

I had a 1988 Suzuki LT250R QuadRacer, I am at 4300' and my stock Mikuni 34mm was jetted/tuned as such:

air screw 1-5/8 turns out
pilot jet 37.5
needle 2nd clip from top
main jet 210

It would start right up and idle all day at 1500rpm, I remember the idle screw being right in the middle of it's allowable adjustment