Are cheap Chinese carburetors impossible to get running right

I picked up a non-running NX125 last week, not noticing it had a cheap Chinese carb on it. It's now running, but far from well. It runs ok up to about half throttle, but more than that, the engine sputters and stalls, but comes back to life, with reduced throttle. I tried a larger main jet but no change.
Am I wasting my time tring to get this cheap carburetor working?

Whilst cabs are very precise pieces of kit IMHO if it idles ok and runs ok at small throttle openings then you should be in with "half a chance" Have you tried removing the air filter and are you happy the exhaust isn't blocked in some way

Not a waste of time. That said, it's pot luck as to whether you get a good one or bad. I'm running one on my KZ440, and it's fine. However, I've seen videos of people with Chinese carbs with bits missing, brass parts wrongly machined so they're coming loose, etc. Don't think these issues are common but they can happen.

Have you taken it completely apart and checked? I mean, as far as the mechanism goes, if everything is returning to position, moving through the full range, no obtsructions, etc. then I would just continue to tune it normally.

Yes, I did a complete tear down and cleaning of the carb. At this point, I need to figure out if it's too rich or too lean at full throttle. Come to think about it, I didn't try partly closing the choke and see if that helps or hurts. I'll also try running with no air cleaner, maybe even no muffler.
Right now the bike is tour down, I had the frame strapped to a tree over the weekend, straightening the frame. This bike hasn't been one of my better buys.

If the bike picks up when shutting the throttle it usually means the top end fueling is too rich so going larger on the main will make no difference and you probably need to go smaller.

most of the Chinese stuff is Garbage, don't add to their balloon fund buy purchasing this crap.