I agree that a rebuild kit probably wasn't any part of the solution, luvpsi. I suspect, though, that the fixed jet you found underneath that blanking off screw on the Ruixing is actually the idle jet, not the main jet. You might try removing it, inspecting whether it is blocked, cleaning it, and blowing carb cleaner through the passageway containing it. In other words, it may be just like the one I posted except for having a rotary valve instead of a throttle butterfly, but it probably has idle ports anyway, so the carb cleaner will gush out from near the edge of the rotary valve.
If you carry out this check, please post the outcome here. I'll leave the thread open.
Incidentally I am not questioning your decision to put a Walbro on your trimmer instead of the Ruixing, because you know that will work well, but it will be useful information for our other members, and our archives, if you post an outcome. If cleaning the idle system makes the Ruixing burst into song, other members will be able to save their money on buying a new carburetor.
