All wheel drive dirtbike

[El Matador]

Want!

http://www.christini.com/media.php?s=videos&m=145

[Popeye the Sailor]

I hate hate HATE websites that automatically play videos, with sound, and with the sound cranked. Window closed in .2 seconds after opening. 

[Oldfisti]

They run bikes like that in Dakar rally.

[Rameses]

I was hoping to see one of those guys do a stoppie past the balance point and then accelerate out of it.   

[The Don]

I think Yamaha WR 450 has a system like that.
http://www.mcnews.com.au/Testing/Yamaha/WR-2trac/Page1.htm

[Hank]

WHAT HAS SCIENCE DONE???

[MTBryan]

I've ridden my dirt bike in the snow quite a bit (I am from Colorado). Even in more than in that video.  With good tires and a good rider, you can really rip it up in the snow. I don't think the 2wd helps all that much in that situation.
Plus, there would be a weight penalty.
The extra weight, cost,  and added traction in about .1 percent of all off road riding situations wouldn't be worth it IMHO.
If it were viable and useful, they would already be racing them today. Not like it's a huge leap in technology.

Ah, just saw the second link. Yes, it actually might be nice in the sand. No more front tire pushing in the turns.

[derby]

I think Yamaha WR 450 has a system like that.
http://www.mcnews.com.au/Testing/Yamaha/WR-2trac/Page1.htm

yup.. it was a system developed by ohlins/yamaha.