For this achievement you have to finish Magma Rift Expert under 5:00 in time attack mode. Make use of the gear part "Speed" to get this. Hardest thing to do is the big curve at the end.
For instruction I made a video. Enjoy and good luck!
I had many problems with Kinect here, I hope it's okay for you. ^^
Also I forgot to make a video when I get the achievement. This is a video where I beat the 5:00 record without the achievement.