via http://wii.gx-mod.com/modules/news/a...p?storyid=3204

Wii hack no end of surprise and shows once again today by offering no less an alternative to official servers online, Nintendo has not seen fit to keep online longer (the Access will be cut May 20, 2014). This multi-platform software (Windows, Mac, Linux) allows to patch your iso Mario Kart Wii (game official or derivatives hacked) so you can connect to a dedicated server alternative set up by enthusiasts and developers very gifted in this area. So you can again enjoy the pleasures of online multiplayer. It is stated that this is a version that is still in alpha stage, which may still contain bugs. Nevertheless, the results of the test team are very encouraging: the battle and versus modes work both in private mode, regional and worldwide. Citation:
My test team played versus and battle in rooms, in regions and worldwide. We played Mario Kart Wii and standard Wiimms MKW-Fun


Note that a generic patch is available for patching other games with online mode. Feel free to visit the official website to learn about opportunities but also rules governing these alternative servers (the cheating may cause a ban, unless the parties to any private with knowingly). System also allows the use of friend codes ... to be tested here wiimmfi-Patcher for Mario Kart Wii wiimmfi-patcher (generic)