You wanna use Aperture Priority at the biggest aperture of your camera (2.7 in my S3). That way, the camera choses the fastest shutter speed.
As PyrePhox says, focus to infinity but if you use Manual mode you will have different exposures due to the light conditions.
Then play with the ISO, I recomend 200. I really hate noise but you will preffer a noisy picture than a blurry picture.
This pictrue was taken riding my bicycle approaching Blackness Castle in Scotland. Using AV=2.7 and the resulting shutter speed was 1/250. Enough for moderate bouncing. I could get a good expose of the castle despite its name!
Regarding your set up on the handlebar, I know it is the first place you think about and the must confortable but in fact it is the worst. If the camera is fixed to the scooter, the vibration and bouncing is just too much. You have to hold the camera yourself so your body acts like a chock absorber. You can use a strap around your neck and press the sutter with the right hand, I don't know if driving a scooter with one hand is difficult. At first, I fixed my camera to the bicycle handlebar but could never get a sharp picture. What I do now is put my camera in a handlebar bag so it is easy to reach it when I see something worth photographing. I know you want a pic/sec and a camera on the handlebar but it's very difficult IMO.
Hope it helps.
