Need help. Critique my picture

I took some pictures of an indoor Arena Cross in Dayton. I am a rookie with a DSLR and I need to some help of what I can do better next time to improve my picture taking. I see too much noise in my picture. I understand that my iso is at 800 but with the bikes moving I had a hard time get brighter pictures without the higher iso, or I am wrong. I have the 18-70mm kit.

http://www.pbase.com/baukerman/image/38933690/original

iso = 800
white balance = auto -3
shutter = 1/250
aperture = f4.5