by jet I believe you are talking about the main jet that screws into the holder? If you are using 190 (hex head) its is very very large, the jet you need to use is 150, the other major factor usually on a junkyard carb is corroding of the inside of the emulsion tube housing,you would have to take it apart completely - and check for salt like deposits on it, also check the air bleed from the air inlet throat to the emulsion tube - if its not clean your fuel will not foam up in the tube and you may see loss of power and an over rich mixture at mid throttle. I am assuming you are using the right needle jet with proper clip position.
and 1.5 turns of the idle mixture is too rich, you need it to be at 2.25 turns outwards with a 17.5mm pilot jet for proper idle mixture strength
My best advice is to disassemble the carb and adjust it to factory specs starting from the float height. use new petrol resistant O rings wherever required on the carb - The jet holder uses an O ring, if that O ring is bad you will have a super super rich mixture at 1/2 to Wide open throttle. Clean the whole carb meticulously with carb cleaner, brush and pieces of fine wire or nylon bristles even the fine holes in the emulsion tube