Sounds to me like the float level is too low. Can you take the carb back to the "rebuilder". Or with a little help from the guys here you could check it yourself.
You could just advance the timing a little using the Octane selector & see what happens. It has a scale on it so it is easy to see what you changed & go back if necessary
I like to adjust the idle mixture screw about 1/2 turn open from the point where it starts to slow down.
Georgeeeeee
