To activate the cheat mode you must beat the highest score on the current continent highscore table (Africa is the easiest). Enter '750J' into the highscore table and press the fire button, it will now change to '....'. The cheat mode is now enabled. Now to summon the cheat alteration menu hold down 'Ctrl', 'left Alt', 'Z' and 'T' while the credits screen changes to the options screen.
After a short while the screen will turn black and it is at this point when you should release all of the keys. If you have done this correctly you will now be asked to enter new values for the outer and inner road turn effect coefficients. You can do this using the numeric keypad. These parameters simply determine how well you handle the race corners. If you enter a high number you will be more prone to skidding off on the corners. If you enter a low number, say 20 and 10 respectively, when you come to a corner at about 300 mph, you can corner with no problem at all, making it far easier to complete a course.
Once you have activated the cheat mode you'll also receive a machine gun! To make use of the weapon just hold the 'left Amiga' key during play. It can distroy all other bikes and road side obstacles.