The biker is riding a dirt bike on a dirt track, navigating a turn.  
The rider is cycling a mountain bike on a rugged trail, negotiating a curve.  
The motorcyclist is riding a dirt bike on a dusty course, maneuvering a bend.  
The athlete is racing a dirt bike on a muddy path, handling a sharp turn.  
The adrenaline seeker is riding a dirt bike on a treacherous course, tackling a turn.