MX Unleashed cheats and cheat codes for Playstation 2

Select - "Options" tab in the main menu, after press R1 or L1 to cycle
from the "Game Settings" option. Do it until you will see "Cheats" option.
Type to here the following codes:

Unlock 50cc Class: Type SQUIRRELDOG
Open Up Pro Physics: Type SWAPPIN
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