powerband,
On the surface this sounds carburetor related. I would check out my heat riser assembly. I think most of these are frozen open, and if yours is, it might be helpful to get it operational to help heat the carburetor quicker.
It might be a good idea to take a look at the condition of the ignition system. Sometimes humidity and dampness go hand in hand with colder weather, and this can cause a "lightning show" with the cap and wires.
As the engine warms up and things dry out, it will return to normal. Some folks will start their rig at night or in a dark garage to catch a glimpse of the arcing and sparking under the hood. Good luck.
Stuart
