I have a 1999 Harley Davidson Twin Cam FXDL. It has a Mikuni HSR carburetor with round air cleaner without cutouts. I have a Screamin' Eagle ignition module and coils. On a recent trip I rode through some serious rain storms. With each cloudbursts the Harley lost power. At full throttle I could manage to cruise at 100 km/h. It felt like the bike was running on one cylinder. As soon as the rain stopped, the bike ran normally. Where do I start to look for the problem? I don't know if I should be looking for water in the intake, an electrical short, or a ground problem.

Are there any fault codes indicated on the speedo? Are the spark plug wires in good shape and connected securely? Cosmetic spark plug and head bolt covers can sometimes cause a misfire. Are the ignition module plugs still sealed properly? Remove the plugs and coat the connectors with dielectric grease to insure a good seal. Check for water or dirt in the engine sensor connectors under the camshaft cover. This connector is out in the open in the direct path of the water that comes off the front tire.