I had a SE with K&N filter and few other mods on my 04 1200. Changed out the SE for a Hammer Performance A/C with 2" wide oval filter along with their Horseshoe Breather Kit. The bike immediately was nosing over when hitting the throttle before it would pick up and when slowing down from highway speeds it would backfire like crazy. Took it to a really good independent guy, he installed a 48 pilot and a 195 main jet. The damn bike is so quick and responsive I'm just amazed. Here is a pic of the A/C I'm running and the Horseshoe Breather Kit.

 

I put a total of 200 miles on last weekend and the bike ran great other than on occasional cough, especially when it was cold. Today was the first opportunity to ride to work and it ran great on the way in and at lunch.

I, of course, took the long way home (35 miles) and everything was fine for much of the ride. I stopped after about 20 miles to check my phone and shut the bike off for a couple minutes. It fired right back up and the idle seemed to be a little higher than normal. During the remaining 10 miles home, I noticed some decel pops and it coughed once or twice when I pulled out from stop signs. The idle seemed to be a bit high at each stop - so I figured I'd have to check the adjustment on the cables and maybe drop the idle adjustment if the cable adjustment didn't take care of it.

By the time I got to my driveway, the idle was noticeably higher almost as if the choke cable was pulled out even though it wasn't. I pulled in the shed and immediately loosened the jam nuts on the throttle cables and began adjusting them in an attempt to slow the idle. The slowest position was with both cables nearly fully extended (few threads showing).

Since the idle was still high, I adjusted the idle screw near the throttle cables counterclockwise about a quarter turn until the idle relaxed to a more normal pace. Following the advice of the Harley Performance site, I turned the a/f screw in fully attempting to make the bike stumble. With the screw fully seated, the bike continued to run about the same. I decided to back the screw out to where I started - about 1 3/4 turns. When I attempted to blipped the throttle, the engine stumbled on a few attempts then shut off. I haven't been able to get it to run since.

After it failed to start, I removed the AC and shut off the petcock. I then pulled each plug and found that the contacts were a nice light tan color and the ceramic was a light burnt orange similar to the photos in the previous post, so they weren't fouled. I put everything back to where I started and let it sit for half an hour. I've made several attempts to start it and on only one occasion it caught and ran for a few seconds before shutting off again. This bike has never given me a problem when starting - even when it sat for weeks in the freezing temps.

Sorry for the lengthy post, but I wanted to list everything that happened. I don't know what to look for first. The weather is supposed to get nice over the next few days and I want to get running again ASAP. I have no idea how things changed so dramatically, so quickly.