Yes, they did make it 439cc for racing rules. Yes they name it 450, not 439. If you look at 90% of everything out there, the sticker on the bike is a rounded off # its never the actual # For instance, my honda 900RR, its a 919cc. My vfr, its an 800, its only something like 778 or something, I forget.
I am glda they didnt call it a yfz439, thats kinda stupid. That would be like callig a 400 a 399. Now when it comes to the yzf426, well you got me!
But that is a very standard thing to do.

 

I wanted to say Thank you to Ridley for all of his comments. They are always very helpful, and very truthful. I enjoy reading what you have to say. I too have a new yfz450, but am away form home right now and wont beable to ride it till I get home onthe 21st of July. I really enjoy reading what everyone has to say, but especailly was pleased to read Ridley's new posts, as I too have a raptor 660, and was very curius how it compared. I was hoping that I didnt make a mistake by buying a slower quad. Doesnt sound like it from what I have read!
Thanks again for all the good info. ~135boom