On my sporty, when taking off from a stop sign/traffic light, it will cough or sputter (no popping) pretty much all of the time. Idles fine and when I jump on it runs very well.
My thoughts are that my middle jet is wrong - this is a 96 carb (can't remember the jetting). Right now it has the stock air filter (which means very little air getting to it) and the screamin eagle exhaust. I am about to replace the air breather with a higher air flow unit, so I will not be making any adjustments until I install it.
There was one oddity - I took the breather off just to check on something - and when I would acclerate it, some gas vapor appears to blow back out of the carb at slight/mid acceleration (standing still). I may sound like an idiot here, but I thought the carb just sucked - it appears to blow, too (lots of possibilities with this thread). It does appear that I am smelling more gas when around the carb then I should.
Any thoughts?

 

Coughing/sputtering like that is a sign of too lean. Check to make sure you don't have an intake leak. Changing the air filter will likely make it worse, if you don't change something else. It is normal for carbs to have a vapor cloud as you describe. It is usually inside the air filter so you don't notice it, and the amount may depend on how the motor is cammed.

 

Just replaced the intake manifold gaskets on the bike about two weeks ago. It would appear there would only be two sources of intake leaks on the bike (manifold gaskets and the gasket between the manifold and the carb. Also replaced the hose between the VOES and the carb. Will check them. Working intake leaks on the shovel, so might as well work them on the sporty, too.

 

Do the old trick of spraying some carb cleaner around the joints while the bike is idling and see if the engine sound changes. You probably don't have a leak, but check it that way. After that, change the air cleaner if you're planning on it and tune the slow speed circuit. I don't know CV's, so can't help you there.

Oh, I think I have a gas tank and a seat that fit your FLT. Seat needs new foam (old is really hard). The vinyl was good last I looked at it 10 years ago (brown), tank had some rust inside but not too bad. $20 plus shipping and they're yours.

 

First make sure that the accelerator pump is operating, this is simple to check by removing the filter and with the engine off but fuel on, roll the throttle and see if fuel squirts into the carb throat. If not, check the rod on the left (facing front) of the carb to make sure it is not sticking in the boss that supports it. If so lubricate it. If the pump is being operated then you will need to clean the ports. Remove the pump cover and clean the passages with carb cleaner. Inspect the diaphragm for tears or leaks, replace it if needed.
In either case, the bike will ru,n better at low speed with a number 45 low speed jet. That may be all you need but you will still need to make sure you have an accelerator pump.

 

Checked the accelerator pump. I shoot two squirts every morning on first start. It is a little off center, but that is about it. I plan to pull the carb and verify jet sizes tomorrow - if I can a magnifying glass to read the numbers on the things.

 

Have not had an opportunity to upgrade the jets on the carb. I did finally get in my mounting bracket that would allow me to mount my high-flow air breather. There is some stutter, but there is a substantial improvement in low speed power. Some minor hesitation at take off and I suspect this is where rejetting will make the difference.