I have a 2006 Sportster 1200C with about 10,400ish miles on it and I've been chasing a issue for about a year now. It will start fine, and it runs well for about the first 10-15 minutes, then whenever I am slowing to turn, or stopped and then get back on the throttle the motor will cut-out/cough through the carb/stuttering and spitting. I have replaced the battery, spark plugs and wires, run a few tanks of gas with sea foam through it and today I got it back from my local Harley dealer where they replaced the slow jet in the carb because it was clogged.

When I replaced the plugs I noticed that the front plug looked a little gummed up/fouled out, but the rear looked fine. I made sure that the new plugs were properly gapped and torqued correctly. When I got it back today, it rode fine for quite a while and then it started acting up worse than before I took it in. It got so bad that the motor died in the middle of the street. I was able to eventually get it started and limp home. The new behavior that I notice today was that when it was cutting out and I gave it throttle the check engine light was illuminating. If I give it enough throttle, then it seems to smooth out and stop coughing, but it still seems to happen at each stop/slow down.

I bought this bike used last year and have not made any modifications. The air cleaner looks to be stock and the filter is clean. The pipes are stock, but the previous owner removed the baffles.

Sorry for the long winded post, but I wanted to give as much detail as possible. Does anyone have any idea what may be causing this issue or how it may be corrected?

 

I would guess your carb needs a rebuild kit, maybe float sticking. I would also address the exhaust and get some tork cones or some other type of baffle..maybe dkcustoms can help u out on that.

 

First thing is the two different plug conditions and coughing... this is likely caused by a leaking intake seal. One cylinder is running lean and the other rich. If the dealership didn't replace them when they tuned the bike, they likely tuned it over-rich to compensate for the lean cylinder... that's why the other is fouling. The seals are a few buck$ each and easy to replace, and should be replaced every 3 or 4 years as they harden and don't seal any more. You will likely need to adjust your idle mixture again after replacing them.

The poor running and stalling and lame throttle response could be signs of a bad CKP, pull the engine codes to see if that's the problem. Keep in mind that a bad CKP doesn't always throw an engine code. The CKP is about $70 and you can replace it in about ten minutes.

 

Thanks for the help and advice! I pulled the codes this morning and received a P0374, CKP Sensor Not Detected. Looks like I'll be buying a new sensor, checking the intake seals and the carb. Thanks again!