One of our clients bought a 1993 Harley Davidson FXRP at a revenue department auction. We went over the motorcycle and checked a number of items to make sure the Harley-Davidson FXRP was roadworthy. As it turned out, the only real problem we found was that the carburetor was in a serious need of a rebuild (probably seen to much Ethanol fuel). Though after a bit of standard work the engine would run, it did not respond well to throttle inputs. The correct fix was to pull it off and rebuild it, but we also wanted to increase the Harleys performance. Our solution was to let our carburetor expert for special rebuild and upgrade treatment.
When our expert looked at the carburetor, it gets completely ripped down and cleaned. He then hand-hones the slide and bore of the carburetor so they mate smoothly when the throttle is wide open. Based on the engine that the carburetor will be on. He modifies the carburetor, as needed, the vent hole, spring, needle, main jet, and low-speed jet. He also inspects and pressure tests the diaphragm. The starting circuit/enrichener is also modified so that it acts like a true accelerator pump for better throttle response. When we pressed our expert for his recommendation on what air cleaner to use with his reworked carburetor, he preferred a Screamin' Eagle air cleaner for Evos. We have had good success with this kit in the past, so we were glad to hear it would work well with our clients newly tuned carburetor. As for what exhaust pipes to use, our expert didn't have a specific brand, but he did say not to use unbaffled drag pipes (at least not for we got the license plates).
Once we were done, the Harley-Davidson FXRP ran great, after we made a slight adjustment to the idle mixture screw. Our expert automatically removes the plug that covers this screw when he reworks the carburetor, so you can adjust the idle mixture to eliminate any popping and spitting through the carburetor. This is a common problem on carbureted Evos and Twin Cams due to the extra-lean fuel mix Harley-Davidson must run to pass Thai emission requirements. Our carburetor tuning expert covers the screw with a removable rubber cap.