You can spray WD40 round the gasket and see if it affects the idle.

 

With a cough like that it sounds like a vacuum issue. Maybe when it coughed it blew a hose of a nipple. I have had a backfire through a carb, and it blew the hose right off the intake. Could not see it, but when I started it up. It ran like crap. Finally found it.
Also check the plugs for fouling if you choked the hell out of it.

Forgive the simplicity, but you also said you changed your plugs. Did you change plug wires also? Guy the other day had his wires swapped, and it coughed through the intake, and wouldn't run worth a flip.

 

It is probably bad gas since Dec, goes bad in 30 days w/10% corn.
Makes it real lean, your problem!
IMHO

 

It's always a good idea to check the intake gaskets, as described above. Fresh gas is also a good idea. You should also consider that in cold weather the air is more dense, more O2 molecules per cubic foot, and at the same time the amount of gas is the same as a warmer day. End result, a lean mixture and carb coughs, add to that a leaking intake-(more air added to the lean mixture)- also older fuel and I'm guessing one of them will be your issue.

D

 

Thanks Ill look into the old gas and check the intake for leaks also a old timer said use propane arond the intake less mess then wd40 Also I changed the plugs after she was running like crap Never had this problem before I took the bike ou twice in the last week one day was 70 deg and one day was 45 deg may condensation after riding her for a half hour and then used up some gas condensation settled in after I put it into the garage Thanks

 

its just cold out. mine did the same thing untill i turn out the mix screw a half turn or so. my sportie also did that in cold weather, i call it winter carb adjusting.