Road Kings are made for the wide, open spaces.
Harley introduced Road King dressers with an 82 cubic inch Evolution engine in 1993. The models were sold with 88 inch Twin Cam engines beginning in 1999, and since 2006 the model has been shipped with 96 cubic inch Twin Cam power plants. The current model weighs about 815 pounds. They are designed for long distance travel so riders who do a lot of touring are often concerned with gas mileage. After performing basic stage one power upgrades, more power always equals poorer gas mileage. There are, however, a number of suggestions for improving power without seriously degrading mileage on the road.
1. It is common to call the first necessary power improvements to any new Road King the “Harley tax.” The Motor Company inhibits the respiration of new motors to better meet government clean air goals. The first power improvement you should make is to your Road King‘s air intake. Replace your stock air cleaner with a high flow air cleaner.
2. If your motorcycle is carbureted, rejet your carb, remove the factory installed air-fuel mixture plug on the bottom of your stock carburetor and fatten up the mixture slightly. If your bike has Electronic Fuel Injection, replace your EFI module with an aftermarket model or at least have your stock EFI remapped by a competent technician. Research done by Harley-Davidson in 2007 showed that Road King horsepower could be increased by about 9 percent by remapping alone.
3. Install a high performance, two into one exhaust. What the engine breathes in it must also breathe out. Installation of an efficient exhaust system can also add another nine or ten percent to your engine’s horsepower. Two into one exhausts help maintain equal back pressure in both cylinders. Replacing your Road King’s exhaust is a basic job you should have no trouble doing yourself.
4. If you spend most of the time on your Road King touring, you should consider a replacement cam or cams. Cams control the flow of air into and exhaust out of your cylinders. They also influence the power range of your bike. If you spend most of your riding time going 80 miles an hour through the wide open spaces you want your Road King to make power most efficiently in that power band.
5. Consider replacing your stock cylinder heads with aftermarket cylinder heads. Head design and porting is a craft that is difficult to perfect with mass-produced products. The shape and finish of your heads greatly effects efficiency of the explosions in your engines. Bigger bangs mean more power. Most after market head makers and porters claim power increases of up to ten percent with their products.