Have you tested the fuel pickup line? They do develop pin holes sometimes especially those molded curly versions. Also check for vacuum or air leaks in the crankcase and the intake.
Just started seeing some of the Ruixings here and I had problems with them operating correctly. I even had one that was a replacement on a Poulan leaf blower that had to the choke butterfly modified to even work right. The original carburetor would not even pickup the fuel and the replacement would flood the engine at start up on the very first hit. I just happen across what was causing the problem.
