Hi guys 
I installed a rungtong carb on my dt 125 1974 as I didn’t have an original one , bike starts fine but has problems at mid to top throttle,, I tried to change the main jet but my stock of original makuni and none original jets wouldn’t fit ,,, the screw thread was different sizes , I just can’t seem to find on eBay or anywhere any jets to fit !! It’s so annoying, can anyone help please ? I would buy an original carb if I could find one ,, thanks guys  

Rungtong, at least its got a name, don't think mine had anything. Gettin serious though, have you tried leaning out the pilot & dropping the slide needle-raising the clip. I did change the main on mine but was a while ago so not sure if i changed the mikuni jet thread but think i actually ran a tap up the spout to change needle jet to close enough to screw in a mikuni. mine is a 175 top end but originally a 125.
I guess if you never had a carb the you don't know how it ran prior. Just saying that to bring up the possibility of a restricted exhaust or other multiple things, bur from what you're saying yep it sounds over-rich, which exhaust can do if blocking up on full throttle--just saying, Cheers.