this is what zwebx was talking about, no you cant rego a yz250 or crf250r due to the fact they were built for motocross so they dont come with a compliance plate, when i was working at the local yamaha dealership we had a 2014 yz450 getting kitted out with a rec rego kit in then shop, it just needed to be wired up... and also you usually find that "motards" that were made for recreational use not commuting everyday, they ussaully go through gearboxes pretty quick...
yeah as far as i know the crf250x and the R are pretty much the same other then performance parts to help the R model abit and the X model having elec start and ect ect....