Put in the following codes for your name. Most of these have a period before them:
.meet6 - all 6 meets
.lapt18 - 18 best laps
.prix - GP mode finished
.test9 - all 9 driving tests finished
borkbork - unlock everything
.RESP54 - set respect points to 54 (Change 54 to the number you want)
Boost start
To do a boost-start you just hold X and A from where it shows the racers to when it says "1" in the count-down.Then let go of X (but continue holding A)and your bike will boost forwards.
Get new bikes and levels
To get new levels and bikes you have to beat meets. I haven't gotten all the bikes or levels yet but I'm working on it.
Grand prix mode
Go to time attack and beat the best record. This will unlock GPM FOR single & mult.