Do a wheelie. Preload while doing the wheelie and release Powerup. You will do a backflip without going off a jump.
Bonus ATVs
Successfully complete the ATV Academy Training and Trick Training to unlock the Dimension and Viper ATVs. Win over eight races in arcade mode to unlock the ATC ATV.
Drive into wall
In multi-player freestyle unlimited mode, drive up on ramp that says AC racing upper slanted wall with red stripes. Drive right until you see the vent on floor that is lit. Do a stoppie (press Analog-stick Up + B) and slide into the vent. If done correctly, you will crash and be reset facing the wall. Press A and drive forward slowly. You will see purple and your ATV will become small. You can do tricks and rack up points, but you cannot exit and keep them. To escape, stay upside down until you fall. Do not press L or the game will freeze.
Get ATC
Come first in eight arcade mode races.
Get Dimension and Viper
Finish ATV Academy Training, and also Trick Training.
Quick Turn
When going fast and are trying to turn, use the speed boost while turning. The bike will seem to jump forward.
Super flips
Go to the freestyle level. Get your boost all the way up. Start going around the course to get speed. If you choose to use the loop as your take off, you need to boost all the way around it. Another good ramp to use is the one that is sort of under an elevated ramp; you will not need boost. To do many flips, choose your ramp and get speed. When you are about 20 feet away from the take off, hold Analog-stick Down. Keep it held and when you get to the peak of the take off, you will do many flips.
Various Cheats
Enter the following names for your profile name to get the desired cheats:
Code - Granted wish
REDROOSTER - Get Champs
DOUBLEBARREL - Get Challenges
ROADKILL - Get All Tracks
BUBBA - Get all riders
GENERALLEE - Get all ATV's
FIDDLERSELBOW - Get all Tricks
GINGHAM - Max out Stats