Trials Rising

At CHECKPOINT 9, which is marked as such in game and comes immediately after riding over the floor panel which pulls out a wall section to propel you uphill, simply reverse.

You'll fall down a hole a begin an Indiana Jones style puzzle of sorts, although there are plenty of checkpoints during this.

To complete this short section, ride forwards onto the button which will shoot you upwards. Roll back from the right hand landing point onto the left hand one to avoid being crushed into the roof, then ride forwards underneath the landing which tried to crush you.

Follow the next section until you reach a point where you can't continue, the roll slowly backwards to land on another moving platform. Again, ride through to avoid being crushed, and when you reach your second dead end, drop backwards and ride across the moving platform.

The prize is a golden squirrel, and your achievement!

I did this on the Donkey my first time through the level - it shouldn't be difficult on any bike.