I currently have 4, 2 stroke engines on 4 seperate bikes. Every one is different as far as cold starting is concerned. One likes full choke and a little tickle. One wants half choke, no tickle, the other two will start with no choke at all and no tickle but one starts immediately and the other wants a few feet of pedaling. Go figure. I've switched carbs but the engine seems to dictate what it needs for a cold start irrespective of what carburetor is on it. They all have the same plugs, plug wires and all run on 100:1 Opti 2 oil. Weird little buggers, aren't they? It just takes time and a little experience to find out what your particular engine requires for cold starts. Good luck.
Tom