This engine is brand spanking new going into a brand new car, so it shouldn't have any air leaks or need a new carby.
We have however found that the low speed needle was pre set at one turn out from closed, the instructions say 2.5. Reset that, but still didn't change anything.

It will start easy, run for maybe 3-4 minutes at slow speed then stop, and it cant restart, if you listen it sounds like the fuel is boiling inside the crank case. Head temp at the glow plug is 240deg F at that time. Temp guage has been checked and is accurate