We already have an official thread for Friend Code exchanging, Mario Kart included. Please use the thread below or the General FC Exchange Thread instead, as posting in duplicate threads is responding to spam, and thus against the rules..
^ Mario Kart Wii Friend Code Thread
You can also use the following thread for exchanging any other Wii games' Friend Codes.
^ General FC Exchange Thread
Also, would you mind reading the rules? Thanks!