The flat head screw next to the primer is your low speed mixture. Try turning it in til it stops then screwing it out 1 1/2 turns. Also, put the air filter screws in the carb even without the filter assy. They are a part of the primer bulb circuitry. Real brilliant..... and my carb situation was the same with 3 different Tecumsehs. I had 5 different of these as a kid when we first got into karts. My neighbor had a Dingo and i had a 2 seater Manco, then we just got to know those motors so we swapped them onto other stuff. Glad i found the clone nowadays. I have a ton of Tecumseh stuff to sell cheap but nobody wants it.