-( Story related, cannot be missed )-
The following are needed to clear this objective: Ricky's ramp (story related), a booster (from a random biker in the Mine Road), and an auto hover fan.
The hover fan can be found by returning to Nestor and Bolus's vehicle and using the tire iron near the back, where the fender is. This will open the compartment where the fan that maintains the hover car's hover ability can be acquired. Use that fan on the bike to install it properly as an after-market attachment.
With all three goals met, return to the gorge and attempt to drive over the ramp, netting you a cutscene where he drives over and a trophy. * Do not skip the cutscene or else you will miss the trophy.