Cold starts on only a few cylinders

[Burgs]

It's a Pond aluminum KCraft 482, Pro System Carb, msd 6al, blaster 2, and under 500 miles. This thing has been starting without hesitation, all summer. The last few times I started the motor it's been in the mid 50s. It starts and runs on what seams like only a cylinder or two. Rather than let it stall, I slip it into gear and roll away slowly. Every 1/8 mile or so additional cylinders start firing, and as things warm up everything smooths out and it runs smooth as silk. Yesterday, maybe 60-65*, it started on maybe 5 or 6 cylinders, and rather than roll away, I held it at about 12-1500 rpm, and as it warmed up, a minute or two, it smoothed out. I rolled out and had an hour and a half ride, smooth as ever.

Could this be the lack of a choke causing this? Anything else to look for?

Thanks,
Brad