I want a nikon camera! I'm a young photographer! I take photos of motocross to family

Price is not an issue

You want a DSLR. All Nikon models are good cameras, so I wouldn't worry about that. Go to a brick and mortar store and ask questions so you won't be buying a camera with too many features you will never use. The one feature you absolutely need is manual focusing and exposure. That way you can pre-set your exposure and focus for a spot on the course and take your pic when the racers go by that spot without having the camera take time to measure light and focus for you. When you take pics of the birthday party or your significant other standing in front of a fountain or whatever, the auto focus and exposure is just fine, but you'll need manual control for the action shots you want to take.

I'm to a young learning photographer. I purchased the nikon d3100. Not to expensive and great outcome. Its easy to use and would be perfect.

Price is not an issue? Really? Sounds good to be you right now.
Capturing a motorbike will require a fast shutter speed and to keep a safe distance you will need a zoom lens, possibly telephoto.
You will probably find yourself wanting a good tripod and as you are outside, a lens hood to keep the sun off the lens.
As for the camera, I would hesitate about advising you to get a high end camera until you know about photography.

The Nikon D3100 is a nice entry level camera and you won't really go wrong.

But if you want to take shots of motorcross then the D3100 will limit you to 4 shots per second on high speed multiple shot mode. Actually that's not bad at all to be honest.

But if price really isn't an issue, you might as well choose a D7000 with six frames per second!

Only if price isn't an issue mind you.

There's a nice motorcross shot below…

You could go more, but it's just not necessary for a beginner. D7000 is a semi-pro camera and very very nice.

Price is not an issue? I want to be in your shoes right now: P

I personally use a Nikon D7000. I love it but it's kinda a higher consumer rated priced camera, but everything about it I love.

It's also good for motocross, I shot my dad motocross races with it as he is sponsored and it works out great.

But its a semi-pro camera, if you're a beginner or amateur then I would recommend the good ol' Nikon D5100/Canon 600D they are really good beginner/amateur cameras and would still fit your needs and more. Remember you'll need to buy a good glass as well, and since price is not an issue then you can buy a really good glass with a Nikon d5100 and your set for awhile!

Get a d3x and a d3s I have both and they serve me very well
Price isn't an issue though so maybe get a hassleblad too…
Price isn't an issue… Really.