I did the offroad sections last year on my 660X (my avatar picture at the moment is me on the actual off road part), from what I saw he would have no trouble at all on a 125 offroad. He may even be better off than I was, lighter etc. you cannot go fast enough with road tyres and very bumpy sections.

There was one part I had to stop and watch others first, with road tyres on I just gassed it through and it made it no problem. I think the 125 would easily make it as well.

Overall the offroad bits would be ok but its the onroad bits I would worry about. The NavXT was fantastic (I wish I had a bike at the moment), some of the hills and views were amazing, just dont know how good it would be chugging away up some of those hills we did. The 660X blitzed it all. That said the sheep were in lots of places so you had to ride with that in mind all the time.

Finally make sure whatever he gets he and it are water proof....!

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