Honda has a nice collection of their motorcycles, on YouTube, only a small portion which are off-road motorcycles but still a very interesting collection and I hope more will be added. Above is a Honda MT125, one of the 2-stroke motorcycles they built although they are known mostly for 4-strokes. To visit the collection and browse more motorcycles, use the button below.
Geoff Ballard explaining the various options to avoid flat tires when riding offroad. This will be applicable to both modern and vintage off road motorcycles.
More than a story of the Suzuki PE, including a nice retrospective of the times and the other 175cc Enduros that were popular. A pretty good watch if you can deal with all of the advertisements ;-)
I'm partial to Hodakas, I always found them interesting and eventually found a Road Toad 100 project bike that I've spent little on but have been slowly fixing up - not a full restore - yet!
This article details another Hodaka called Navajo'daka and I think it's a pretty succesful design.