Could dirt bike racing be deducted from taxes?

Yes, it can. I can only speak of the side of being a moto parent, regarding my son's racing. But as parents, you can sponsor your child's racing (as if we don't anyway!). But on paper, parents can write it off as an actual sponsorship. No matter parent or racer, gas can and should be written off. If you are a racer in A class, technically you are supposed to pay taxes from your earnings, but tracks don't fill out a w-2 for A class racers, so I have never understood that. So, my point is, if you are in A class, you can write off everything from your bike to your grip doughnuts. Good luck, bless your racing.