Help identify the problem
 

I have a 2005 RKC. It is set up with a Fuel Moto Tuner, Samson Fishtails no baffles and Arlen Ness Stage 2 big Sucker. Same set up for about 3 years going. Over the past 2 weekends I have noticed something new. I can be going down the road 55 + mph and it runs fine. I have noticed at low speed(50mph and lower) mostly in 5th gear and sometimes shifting up through the gears at low speed. This is also when I barely have the throttle on( just enough to open it ). I have noticed the bike " coughing and struttering" and an occasional backfire, but when I roll on the throttle it runs smooth. Battery and connections are good, plugs are new, a/c is clean.

Have you performed a fuel pressure test and verified it holds pressure after key off?

I have not. I won't be able to get it to my mechanic til next weekend.

Does it get worse as the fuel level gets lower?

I am going to keep an eye on this thread as I have exactly the same issue on my 2009 Sporty.

Runs fine under throttle but the moment I ease off and commence cruising it starts to miss and jerk a lot, but If I give it more throttle she is fine.

Did notice that the problem is way way worse/more obvious when running a stage 1 air cleaner. If i swap back to the factory air cleaner setup the problem is still there in the background BUT far less obvious/impacting.

So far have replaced the IAC with no improvement. I have not inspected the fuel pump or filter yet.

Issues with leaking fuel lines inside Touring bikes weren't common to XLs. If you can turn the problem on and off with the less restrictive air cleaner it sounds lean and that begins a slightly different diagnostic path.

Help identify the problem
 

Why would you lug the motor in 5th gear under 50mph? That would be enough to cause coughing and stuttering.

That is a very good catch. When he said sputtering I took it as misfire. You may be on to something here.

ED ... No it is at any fuel capacity. GolfBlues.. I would only lug it down while riding in a group if I caught up to the person in front of me too quickly. It happens even shifting up through the gears like pulling away from a stoplight and going easy. I do get a backfire every now and then.

Well, one thing if it truly a misfire it should probably throw a code and you could pull that up in speedo diagnostics.

Wouldn't be the first bike of that year to have a broken injector wire right at the connector due to a tight harness on the backbone. Try wiggling the injector wires while its idling on the jiffy stand and see if you can duplicate it.

If the wires are really tight, that's bad.