I've been looking at a lot of different forums, and the 400's seem to be all cold blooded when the weather gets cold, mine is the smae way. I started using methyl dehydrate, cause I thought it might be a water problem due to the heating/cooling of the carb. Didn't seem to have any effect on it starting though. I screwed with that idle adjustment almost continually while operating the choke. I finally settled on a setting for it, so I leave it alone now. Idle speed is supposed to be 1250 RPM, can't tell without a tach though. I use full choke, 'till it begins to "chug", then back it of slowly. I have to use partial choke, or just off the stop, until the motor warms up enough to run normally. Pain in the A**, but that seems to work for me.
I don't think the motor ever gets hot, maybe I'm just not working it hard enough, but I've only ever had the fan for the oil cooler come on once. Wonder if it still works?

 

hey liquidplumer didnt mean to sound like and *** or anything i was just joking around with ya