If your Ultra is fuel injected ,you may need one of these.
Harley Ultra may refer to several motorcycles including the Tourglide Ultra equipped with an Evolution engine and the Tri Glide Ultra and Electra Glide Ultras with the Twin Cam engine. The solution to your problem is the same no matter what Ultra you ride. One of five simple-to-fix things is probably wrong. The most likely problem is your idling speed is set too low. It is also possible that your fuel-air mixture is set too lean, your plugs are fouled, your spark plug wires are loose or defective or that your original equipment vacuum petcock is defective.
1. Diagnose all engine problems by first reading your spark plugs. Access the spark plugs on the left side of your motorcycle. Remove both front and back spark plugs with a spark plug socket and a socket wrench and examine them. If the electrodes are intact and light gray to pale tan, your fuel-air mixture is fine. Reinstall your old plugs. If the electrodes are visibly corroded, your fuel-air mixture is too lean. Replace the old plugs with new ones. If your plugs are visibly sooty, your engine is running too cold or too rich, because you are making too many short trips or because your fuel-air mixture has too much gasoline and not enough air. Replace the plugs with new ones.
2. Inspect your spark plug wires and their connections to the coil and your spark plugs. Plug wires are not moving parts, so they do not usually wear out. If you see visible signs of wear, though, replace them.
3. Adjust the idling speed on a carbureted Ultra by using a small, flat-head screwdriver to turn the adjustment screw on top of the carburetor by the throttle cam. If you have trouble finding the throttle cam, stare at your carburetor while you twist your throttle. It is the part that moves. Adjust the fuel-air mixture on a carbureted Ultra by turning the fuel-air mixture screw on the bottom of your carburetor. The correct adjustment should be between two-and-an-eighth or two-and-a-quarter turns out.
4. Adjust both the idling speed and fuel-air mixture on a fuel-injected Ultra by using a Screaming Eagle Race Tuner, which is usually called a SERT, or equivalent, and a laptop computer. The SERT comes with software you install on your computer and cables that connect your laptop to a pigtail connection next to the electronic control module behind the side cover. Remove the seat screw behind the seat with an Allen wrench, then remove the seat to gain access to this pigtail connection.