The carburetor is most likely a Chinese copy of a Walbro and just has the name Tillotson cast on it? They normally work well.
Also your running description sounds like the no advance or all advance of a model #4 RCEXL ignition module. They didn't have a advance curve. But likely the ignition module is also a Chinese copy of a Chinese RCEXL ignition on a Chinese engine that is a copy of another Chinese engine?
Enjoy