Get 100 level in sp and unlock all bikes and riders.
1.- Backup your DATA.MIX file in your game folder.
2.- Unpack 100Level&Unlock bikes and riders DATA.MIX to your game folder and overwrite.
3.- Go to a race and finish it in any position, it should give you 100 level then.
4.- Let the game autosave and quit.
5.- Restore your original DATA.MIX file.