Confirmed, PAL Mario Kart Wii is working on Jap Wii.
Imgburn
3.2J Wii
Wiikey 1.9g
I first used WBB to remove the update then burnt to disc. Do this otherwise you will get dual channels.
Tip: Use re-writables that way you won't waste media
I also updated first from when i played Jap SSBB