The behavior you are describing sounds like a lean flat-spot, on transition from curb idle to main jet operation. It appears that the person who overhauled your carburetor did NOT know what he was doing.
Did you save the carburetor parts from the overhaul? You may need them to restore performance.
Let me give you the full benefit of my experience when I say to you
"If it AIN'T BROKE, DON'T FIX IT!".
When you decide to overhaul a carburetor, make sure you have the correct parts and overhauling kit or you're in for trouble. You should also make sure the person undertaking the job really knows what he is doing.
Also a routine repair is not the time for you (or your mechanic) to learn how to fix carbs.
The agreement should be that if he can't make it work right, no PAY!
There are too many unscrupulous individuals out there taking advantage of people.