Enter the following names for your profile name to get the desired cheats:

GOLD DUST - Get Everything
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

Easy Turbo  -  When going off a huge jump do a 360 by pushing the direction stick right or left and do two tricks while doing the 360 degrees move. The better the tricks the better the boost.

Master code:  Enter GOLDRUSH as a profile name to unlock all riders, ATVs, tracks, and bonuses.

All riders:  Enter BUBBA as a profile name. A message will confirm correct code entry.

All ATVs:  Enter GENERALLEE as a profile name. A message will confirm correct code entry.

All tracks:  Enter ROADKILL as a profile name. A message will confirm correct code entry.

All tricks:  Enter FIDDLERSELBOW as a profile name. A message will confirm correct code entry.

Maximum stats:  Enter GINGHAM as a profile name. A message will confirm correct code entry. Note: This also increases the stats of your opponents.

Champs:  Enter REDROOSTER as a profile name. A message will confirm correct code entry.

Challenges:  Enter DOUBLEBARREL as a profile name. A message will confirm correct code entry.

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.

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.

Use the following trick to do three or more flips on the ground. First, do a wheelie then keep it held. Hold Preload (R), and when it is full, release it. While holding Analog-stick Back, you will do three or more flips.

Quick turn:  When going fast and are trying to turn, use the speed boost while turning. The bike will seem to jump forward.

Backflip without going off jump:  Do a wheelie. Preload while doing the wheelie and release Powerup. You will do a backflip without going off a jump.