Good Morning,

Live on an island (WA state) but recently took my '91 B2200 (carburated) to the mainland and put her through her paces on the freeway. After an oil project (went from 15W-40 to 10W-30, then back again due to ticking) I've noticed that upon cold startup in the mornings that it starts REALLY rough but eventually smooths out as I throttle up to 1500-1750 rpm. After warmup it's fine, no warning lights. All fluids are holding fine. I give two full pedal pushes before cranking over.
Other symptoms on the initial startup seem that the engine is vibrating quite a bit until smoothing out, also get some "puff" sounds out of the exhaust. This all lasts for a few seconds.
Now I am not a carburetor expert but I suspect it has something to do with that, moisture build up in the fuel filter, or possibly the spark plugs?
Hard to figure out as she runs great afterwards.