You can race it.But there are better choices. Too fat.
That depends on what type of racing you're planning on doing. If you plan on doing desert or supermoto on a track with long straights and tight corners, it's better to start with a WR and strip off some weight than a YZ and having to buy new tranny parts and split the cases (an option that's not even possible with a '10+ YZ).
Or, you can go to a KTM EXC or XCW, but they weigh the same as the WR and cost more.