Check this thing out prospectors!

[Wishfull]

Wait till it loads, and watch the video!
I can see these being very useful!

http://newatlas.com/taurus-2x2-2wd-fat-wheel-motorcycle/44616/

Looks great. Being a Honda motor you can source parts easily enough. I can see you might need to paint it a brighter colour. Being green you'd loose it up there. Don't know how the rims would fare if you got a flat. There's no suspension. Maybe put some of that no flat goo in the tyres.
So did you get one ?

 

[Sacredsite]

Saredsite. How is the front wheel driven. Is it a hydraulic motor or something ?

This will explain it.
https://www.youtube.com/watch?v=si-bI84SZKA

I almost forgot about this one
http://www.ubcobikes.com/au/