Edit the logo on a custom bike to read "kingpin".
To unlock some mini-games (the ones from Moto GP and a couple others), go into options menu and watch the text (not video) credits. Scroll down until you get to the credits for the mini-games. When it appears onscreen, press A. If you entered the code correctly, the screen with the "Mini Games" title will have the "A" in "Games" change to resemble that found on that controller button.
Win the championship on the champion difficulty setting to unlock the legend difficulty setting.
Get 250,000 points in stunt mode to unlock Alex Barros.
Get 100,000 points in stunt mode to unlock Carlos Chera.
Get 500,000 points in stunt mode to unlock Max Biaggi.
Get 750,000 points in stunt mode to unlock Tohru Ukawa.
Get over 1,000,000 points in stunt mode to unlock Valentino Rossi.
Get 325 championship points to unlock the "Edgy" option.
Get 375 championship points to unlock the "Pop Video" option.
Get 300 championship points to unlock the "Saturate" option.
Get 275 championship points to unlock the "Turbo" option.
Successfully complete all the championship challenges to unlock the Sheridan track.
Win first place on any track to unlock that track's highlight's FMV sequence.
Start stunt mode and win the race under the pro difficulty setting. Burn out at the start until the counter reaches about 3,000 and do not go off the track (or you will get the clean section). Do this for about eight tracks to unlock all the characters. Note: You will need a bike with at least all stats at about halfway on each bar.