If you have an adjustment screw for the secondaries and you adjusted your idle using the primary screw you probably exposed the transfer slot too much allowing fuel to dump in at an idle. Pull the carb and check to make sure the primary butterfly is closed enough to make the transfer slot appear to be squared on all 4 sides. Then use only your secondary adjuster for your idle. Its an easy mistake to make. I did it my self when i started using a race style carb.