4-Stroke 450 EXC Six Days
I had the most success using this bike.
Australia Pro World Championship
Hold either the A or B button while your bike is in the air to perform a stunt. Hold the stunt button for most of the course to build your stunt time. Front flip and back flip as often as possible. Stunting while flipping slows your rotation slightly. Each front flip adds 10 seconds, backflips 5 seconds, and if you can pull off a double front flip adds 30 seconds.
the stunt time will subtract time from your total time once you complete the course.
Three courses per location. Your total time needs to be 2:54 or less for the Gold medal. The podium achievements do stack so posting a gold time will unlock the lesser medal achievements as well.