Hmm....I missed where he has a demon. I did not see what kind of carb we are talking about.
As a general rule, the engine needs to be much richer when it is cold than after it warms up. The good thing is that an engine will idle with a wide range of AFR. I never realized this fully until I started fooling with EFI. I just checked my warmup enrichment on my turbo engine. At 80 degrees I run 40% more than the normal amount of fuel at a warm idle. My engine idles at 13.8 AFR because it just seems to like that. That puts the AFR in the 9:1 range when I first crank it at 80 degrees ambient. Keep in mind my CR is around 9:1, cam is 230 dur @ .050 with 114lsa, which all can affect cold start enrichment(choke position for you).
Point of my ramblings is that an engine likes a very rich mixture when it first cranks up. This is what the choke does for you. If the mixture is right without choking then it is WAAYYY too rich when it gets up to temperature.
Just food for thought.