UNLOCK ALL TRACKS

All tracks (you get all the Jet Moto 1 tracks after the first chime halfway through, continue the rest of the code to get the rest of the Jet Moto 2 codes that you haven't obtained yet).

Go to the options screen and set master difficulty plus five laps per race. Go to the one-player select screen, find Li'l Dave and press X. Next go back to the title screen and press Up, Down, Left, Right, R2, R1, L2, L1 within four seconds. Go back to the options screen and set the number of race laps to three. Go back to the one-player select screen, find Wild Ride and press X. Go back to the title screen and press Up, Left, Down, Right, Square, R2, O, L2 within four seconds. Return to the options screen and set the difficulty to amateur, then turn turbos off. Go to the one-player select screen, find Bomber and press X. Go to the title screen and press Up, Down, Left, Right, Up, Down, left, Right within four seconds. Now go back to the options screen and set the difficulty on professional and turn turbos on. Go back to the title screen one last time and press R2, R1, L1, L2, R2, R1, L1, L2 within four seconds. 

Race as Enigma
Go to the options screen and set the difficulty to master and six laps per race. Go to the title screen and press Left, Square, Down, Triangle, Right, O, L1, R1 within four seconds. 

HERE IS ANOTHER SHORTCUT:
This is rather tricky. On Rollercide, there is a place to jump cutting off part of the track. After the first turnaround, where bell is, you can jump through the Chef Boyardee sign and the one to its right. If done right you can land on the upside of the hill instead of following the track down the spiral. But be warned, this shortcut is not easy to take. However if done correctly, you can most likely jump into the lead by doing so. 

To get secret player Monica "Moon Girl" Napolitano, get all the trophies in the trophy case and then at the title screen press X, O, O, R1, L2, O. To get all the tracks press R1, R2, L2, L1, X, X, O, X, L2 within 4 seconds.

In the water just before the third rapid there is a hole in the rocks. Jump over the rock in front of it , don't forget to use turbo. This shortcut is tough but if done correctly may put you ahead a few positions.

In Ka-Ma-Te when you get up to the swamp turbo up the first ramp and land on the yellow bridge above. If you pull this off you will cut a lot of time off your lap.

Just wanted make sure you new about the hidden pass on the Aftershock level of Jet moto 2. It's not really a time saver but it's nice to know. When you enter the section with the criss-crossing streets, go straight through the first intersection and then turn left (obviously). At the next intersection turn right instead of straight and go to the end of the road. Right where you need to make a left one of the turn signs is down and you can go through it. You'll need to weave through two signs and then you'll drop down into that cement riverbed thingy. You'll have to avoid hitting a sign after that and you'll loose time but it's still interesting.