I'd say try a slightly faster shutter speed, use only your center focal point and set your focus to AI Servo. With AI Servo, once you get the rider set in focus you can follow him down the track and the lens will focus with him as he moves. They won't all be perfect but it will increase your odds of getting a few more keepers.
I hope you don't mind I tweaked your photo a little bit. I did a little sharpening and then boosted the colors a little bit. Running them through a little PS treatment can be a big help. It was already a little pixelated/jagged in spots, so sometimes the sharpening brings that out too much. It's best to do it on the original, high-res image first before resizing.