Hello Norman,
Bultaco is early seventies, when in Tortosa bike shop last year he had same bike in different colour, for sale.
Allthough not rusty like english bike would be,  it was completely clapped out. He wanted high price as well , so we could not do a deal in end ! Last time we looked shop had been cleared out , to make way for modern bikes.
Trials bike would seem to be ideal for going up and down barranc, but then I suppose that's what they where originally designed for !  :
Will nead to find out tank range though, as would not want to run out of fuel, as we are miles from any garage, not good in the heat.