Motocross Madness

This can be done in any event type in Career mode. The event types are Race, Rivals, Exploration and Trick session. Mostly likely you will get this from winning a race because in the beginning, not much is unlocked. First time you get a Gold medal for winning the event, the achievment will pop. I got it on the first try, but if your not good at this type of game, it might take a few tries. Just keep trying and leveling up. Upgrading your bike under 'Garage' also helps. Good luck!