I have a 1979 20hp Chrysler mod. 206H9B, I cleaned the carb as it had been sitting for several years. When I first started it before cleaning it would run a few seconds working the choke as it started. So I took it apart and there was crud in needle hole and so forth. I took out the idle screw also when I cleaned it ad after re installing it I can't get it to do much more than just fire and stop. I seated the idle screw lightly and backed it out 1-1/2 turns and tried 2 turns but it won' run. Where should idle be set at? Or I there something else that needs set.