You have two options IMHO. Any suggestions we make may get you closer to running good, but are not guaranteed to achieve that, so you could learn how to tune your carb yourself. Alternatively seek out a local indy who can probably get things just right for you in a darned sight less time. I learned that decades ago!

 

Not going to make any recommendations on jetting as there are too many variables besides mods. Not every bike is the same. As grbrown suggested, play around with the jetting yourself depending on the symptoms, you can determine if your focus should be on main or intermediate jetting adjustments. If your cough happens at high rpm, play with your main jetting. If at low to mid rpm, play with your intermediate jettting.

Here is a good video IMO that may help you with jetting....may not be the same carb or bike but the application is the same. What is helpful in this vid is they show what happens (symptoms) when the bike is running too lean or too rich for both the main and intermediate jetting.

Don't forget to reset your idle mixture, idle speed, and accelerator pump too. There are vids on how to do this.

Have fun with it.....if you learn how to tune, you will have an easier time troubleshooting.

 

The main is rich from the factory. It's the slow and needle that are lean from the factory. A good starting point would be a 45 slow most likely. I'm running an N65C needle shimmed .040 and actually dropped to a 170 main with it on a 1200. I'll have to start over tweaking the carb and timing now tho since I just put the jackhammer 570 cams in.
But you really should start at the beginning because as was said, a lot of variables. An excellent write up on doing this at the sportster only forum in our one of a kind sportsterpedia database.

 

Most of us seem to end up with a 45 pilot jet. Some or all of your problem could simply be adjusting your idle mixture screw. 2 1/2 turns out seems a good starting point for the mix screw, then you can fine tune from there.

John

 

 

 

You may have a Dynojet kit installed. The emulsion tube uses a different thread for the mainjet. You can change it all out (needle, tube, jet), or buy a DJ175 mainjet from Dynojet, or look on Ebay. I bought one DJ175 mainjet from Dynojet ( a bit difficult as I live in CA) and got a DJ180 off EBay (easy peasy). I'm running a 45/175 setup on my 883. I will probably try the DJ180 someday when I open the carb again, but she runs great and plugs look good as is.

John