If you're comfortable with doing so, tear into the carb and see what's going on with the idle circuit. Sounds like it's not getting any fuel. While it was rebuilt, it could have a clogged passage still. Pull it apart, hose down the passages with carb cleaner and blow them out with compressed air.
If you really want to make sure it's totally clean, pull the carb apart, soak is in a 50/50 mix of water and Pine Sol over 3 days, agitating it now & again. After that, hit it with carb cleaner, compressed air and reassemble. The Pine Sol / Water mix isn't hard on gaskets, rubber pieces, etc. You can leave the carb partially assembled, just make sure to blow out the fuel passages.
