Hi, have a 2000 1200 Custom with 9000 miles
Bought it with a stage 1 kit and air filter upgrade
Under steady throttle it lets out an occasional cough
Throttle response seems fine, plugs look good, have removed and cleaned carb, changed intake manifold gaskets and tweaked mixture screw in and out without any results
Any ideas from here?

 

Typical CV cough. A Thunderslide kit helps but they still occasionally have a cough due to a lean condition stemming from an issue with the relation of the slide/needle position in relation to the vacuum of the engine. Most every CV type of carb has this concern from time to time. Richer jetting can take care of it to some degree but you'll then be jetted overly rich to cover up the cough. The lighter Thunderslide and the positionin of the holes along with a different slide spring definitely help. My Softail benefitted greatly from the addition of the kit.

 

Thanks, I think it is a Thunderslide kit that was installed
Have owned the bike 3 years and just started doing it last year
Happens quite frequently until the bike is driven for a while, then seems to be less frequent
Sounds like that's life