The Zama carb I used on a 25cc Weedeater was a C1U also, with M29D & 86A on the side. This Zama has a 14mm throttle bore at the engine side, 9/16" for reference. My carb has adjustable needles, meaning they have screwdriver slots on them. I got 7800 RPMs out of my 25 with a 16-8 M/A Classic prop. It would go all the way to 8k but getting close to being lean. I discovered later that the spark plug gasket was leaking a bit. I fixed that and haven't run it again. My 25 was new and still not broken in yet. I did increase the intake port significantly. I don't think 8K would be possible without this porting. I cleaned up the exhasut port some also, but not as much as the intake port. It is a very smooth running engine.

So with my 25's history for reference, I would definitely try the carb you have. Try and get the needles out and cut a slot, this should be possible. Your exhaust port looks large compared to my 25, but your intake port also seems very small in comparison to your exhaust port. Your carb spacer is different and more complicated than mine was. I was able to bore mine to 1/2" with not much of a problem. I could not take the carb spacer all the way to 14mm, but maybe I could make a new custom one. (Your carb spacer looks like more of a challenge to modify.)

I have several carbs that I just checked with C1U on them. C1U must be a basic casting number for the main body of the carb because the carbs are significantly different.