I like this kind of games a lot, played the flash motocross games a lot while i was at college.
This I liked, but i would have prefer it if it had a faster control, to allow faster turning and moving so you can make more trickier levels. As for level design, i liked it up until the end. Putting the hardest jump in the level at the end of it is frustrating, because you have to repeat everything up to that point (that was fairly easy) and try multiple times. I would suggest not putting this kind of stuff to the end, and move it more like to the 70/80% of the level, so when you make the hard jump you have some downtime to calm down and finish the level. I tried several times and couldn't beat that jump.
Also, i would put the character more to the left of the screen, since you cannot go back, is more important to see what's ahead (especially in that last jump).
Good job!