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XBox - MX Unleashed cheats

Unlock cheat options:
Select  "Options" tab in the main menu, after press R or L to cycle 
from the "Game Settings" option. Do it until you will see "Cheats" option.
Press B to display a keyboard and type to here the following codes:

Unlock 50cc Class: Type SQUIRRELDOG to "Character Completion" option
Open Up Pro Physics: Type SWAPPIN to "Character Completion" option
Unlock all bonuses: Type CLAPPEDOUT to "Character Completion" option

Bowling: WRECKINGBALL 
Expert AI: OBTGOFAST 
Unlock All Machines: MINIGAMES 
500cc Bikes: BIGDOGS 
Freestyle Tracks: BUSTBIG 
National Tracks: ECONATION 
Supercross Tracks STUPERCROSS