Are you using the 1000 yet? If I use that quad, even with the alloutai code, and I can almost lap the others on a couple tracks. Especially the ones with a lot of jumps. The computer ones keep wiping out. I find this game extremely easy compared to a lot of others I have.
What I did last night was use the female rider, and the 1000 with the suspension set to soft, the gearing to max accelerate, and the traction to almost max. The soft suspension seems to keep the quad from airing out so bad on the jumps.

 

I love it,the best out of all the cycle and ps 2 games Ive ever played.FUN FUN FUN.Love the freestyle.2 bad things no manual shift mode,and bikes take forever to getback to racing when ya barrel roll em >Love the heavymetal Music too.happy trails to ya!

 

What quads can you play as? Can you get a Raptor or a DS? It would be kinda cool is those were like bonus quads or cheat codes or something.

 

Blaster
Banshee
Warrior
300EX
400EX
Mojave
Lakota
Scrambler 400
Scrambler 500
A few different versions of what looks like a DS650, but is not named a DS650

The bonus Ravage1000 quad is kinda like a 250R.

 

I just saw an advertizement in this months Dirt Wheels. If you look you can see a Raptor Flying off a jump. You can get a Raptor.