yes the cdi will mess with the electronic cyclometer. to cure this radio shack part number 273-105 which is a snap on ferrite data-line filter cures all problems and i find my cheap speedo is as accurate as my gps and a lot less expensive. the cost of the filter was 5.29 RadioShack.com - Cables, Parts & Connectors: Component parts: Inductive products: Snap-Together Ferrite Choke Core