Track: Gone to Waste
Bike: Pit Viper
Continue through the track until you reach Checkpoint 2 where you will need to preform a backflip onto a small platform in order to beat the obstacle. You'll notice that upon landing on this platform, it will shift downwards. You will need to drop down back onto the ramp you came from, and preform a total of 3 backflips onto this platform which will drop the waste barrel below. Now slowly back off this platform and fall down into the hole where the waste barrel fell, and you will fall into a "wormhole".
Once inside, you'll just need to get the end of the wormhole, which has some difficulty sections. I recommend viewing the video for additional tips on individual obstacles, and making sure to practice if you are struggling. The achievement will unlock upon exiting the wormhole.
*Posting for Maka91, because he is only playing the Xbox One version.