http://www.bumarcade.com/stunt-dirt-bike/game-online.html
Use the motorcycle. There are other versions of it with different obstacles
(don't click on the banner just before the game starts...you'll see the timer countdown when the banner will go away)
http://www.bumarcade.com/bike-mania-2/game-online.html
http://www.bumarcade.com/bike-mania/game-online.html
- J