I have a 96 883 with an S&S super E carb, and straight pipes which has been backfiring out the tailpipes, and fouling plugs. It is just starting to be ridden after sitting for the winter.
I referred to the quick guide on the S&S site, it idles pretty good, but has a problem accelerating. If I twist the throttle slow, it seems ok, but twist it quick and it kinda pauses, then pops out the tail pipe. If I give it a few quick twists, it will almost "catch up". It runs good with new plugs, but after a few miles I start having problems. The plugs are incorrect from what I have been told. They are NGK D7EA, and the bike calls for DCPR7E. Not sure how much differnce that makes. The plugs have been turning a dry powdery black. The old gas was drained out and fresh gas was put in. It runs the same with the air filter on or off.
I checked the charging system, and it's putting out about 14.5v, and the battery is a couple weeks old. The carb was rebuilt last year, and I was told that the bike ran fine last summer. I am wondering if I need to have the carb cleaned, or re-jetted. I have no idea what size jet is in it right now.
Any ideas/suggestions?

 

Change over to harley spark plugs for your bike.Then increase your accelarrator pump shot till the stumble gose away when you whack the throttle.See what happens then.

 

I think the problem is too much fuel when I whack the throttle. With the air filter off, I can see it give a shot of gas when I do that. Plus, it seems to be running rich, judging by the condition of the plugs.

 

Street racer is right about the acellerator pump. And get the right plugs.
Unless you just sit there twisting the throddle all the time this has little to do with a general condition of, Running Rich.
That's the nedle jets

 

That makes sense, because it was idling pretty good, the problem was occuring on acceleration.

 

A super E on a 883?

I'd think too much fuel as well....

 

That's not the first time I've heard that. It was on there when I got it. If the original were still around, I'd put it back on. The bike is new to me, but it was my brother's last summer.