The artwork and sprites in this are fantastic, great job! I particularly liked the animation for running back to the bike after you fall off, that was a really nice touch rather than just respawning.
The sense of speed is great too, the addition of speedlines and obstacles wizzing past works really well and isn't too distracting at such a low resolution. It all feels great to play, especially punching and kicking the other riders and launching them into a tree! :D