Where is the "start" button for the titel screen, when playing Mappy with the wiimote!?
pressing "+" or any other button doesnt work...

To start the game, you mean? You need to add credits. And IIRC, you need to hold "+ and 1" or "+ and 2", either one. Whichever works, press the opposite to actually start playing. You really should look at the Button Config because it tells you all you need to know...

Thanks I couldn't figure out how to start either, I bought this today.

Using the CC doesn't require button chording, Z1 for coin, Z2 for start -- not sure why Namco chose to do it this way; possibly because they could still have + be a pause button...