No cold start/idle without choke

[DBG]

I just bought this bike, and the previous owner called it "cold natured," a very technical term. The mechanical fact is that it won't run unless warmed up. I have to sit and let it run with the choke on for quite a bit before it will idle properly. Once it's warm it runs and sounds great. I noticed right off the bat that the spark plug was bone white, indicating that the mixture was lean. Some cowboy that owned it before me thought he would give this little scooter a pair of balls by drilling a buncha holes in the muffler... :lol: I drilled out that plug on the carb and adjusted the pilot screw. This helped quite a bit, but still no glory without letting it warm up on the choke. I don't really notice any change in the power across the throttle, and it has a pretty good top end (70mph+) unless there's any head wind (~60mph). Is this something that's just inherent to this motorcycle? Or could it be that I need to detail the carb and soak it in some solvent? I mean, this thing won't go two feet without stalling unless the engine's hot. Any tips appreciated.