hi daveb ! i think you've made a good choice with the yam , ive had 2 the older 600 and the newer 660 both great for a bit of green laneing or dirt tracks 
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I have had my Tiber 800 XC in some pretty challenging place - way above my skill level. I t does fine in mud and in rocks; but the rider needs a lot more experience in both! A motocross bike it is not. But it does very well for off pavement riding. Here is a link to my first adventure ride.
https://www.triumphtalk.com/showthread.ph...ational-Forest