So even with new carb, same issues surging?
Confirm you got the correct carb, 16100-Z0L-023 ($15.08)
Confirm all linkage, choke, throttle and governor are correct.
Use a tach and confirm engine speed 2,950-3,100 rpm
Never re-use carb gaskets; old ones can have tiny vacuum leaks.
Be sure gaskets are installed correctly, both in location and orientation
Confirm two long bolts holding air cleaner / carburetor are nice and tight; easy to have a vacuum leak if not
Check fuel tank and fuel link for slime/debris
Fresh gasoline of 86 octane
Air filter new or cleaned
Correct spark plug and gap? BPR6ES (NGK)
These pages should help...