I have a 2003 Fat Boy with 18,000 miles. There is a problem that 3 visits to the shop and $800 has yet to fix. At low speeds it isn't too bad and connectedd to the computer when it isn't heated up looks fine. On the highway the hesitation is so bad that sometimes the top speed is 50 MPH. The black plugs indicate it is running too rich, sometimes. So far the air filter spark plugs and injectors have been changed. Any ideas?

 

Missing info:What has been done to it? You already stated the plugs are black.....soot...oily? Wet w/gas? Where are you on the throttle when it starts acting up? 1/4, 1/2/ 3/4. Run good hot or cold or not at all? What mods over stock? What aftermarket tuning done to it?

 

There isn't much more to include. Everything is stock. When they were replaced the plugs were black and dry. Everytime it is conectted to the computer in the shop it looks fine. As for the throttle, I can feel the hesitationstarting at about 1/3 throttle andit seems to be worst when the bike is completely warmedup, starts fine.

 

Fuel filter dirty and/or pressure regulator weak.

 

Too easy. Already checked. But I also changed the air filter on an off chance. No change