found out see below
The method goes like this: Pop a PAL GameCube disc into the Wii, and head to the 'Disc Channel'. A GameCube logo should be up on the screen. Point the Wii Remote's cursor over the 'Start' option so it's highlighted, and while keeping your hand steady, press the eject button on the Wii. For about one second, the 'Start' option will remain active. In this window of time, hit the A button on the Wii Remote and then swap out your ejected PAL GCN disc with an NTSC (Japanese or USA) disc, which the Wii will accept into the drive.
If you get it right, the Wii should boot up in GameCube mode and run your NTSC game!