Hey Dave!
Right off hand, it doesn't sound like a timing issue. I'm not familiar with your carb, but it sounds like either a carb without a choke, or a carb with a choke that is not functioning.
My webers (no chokes), are a little rough when the engine is cold.
I'm sure someone will chime in that's familiar with your combo.
I guess you've noticed that MUSR6 is coming up....