This is a modified C5 ...
UCE engines are used in quite a few offroad/scrambler mods:
As far as dirt goes, you really do not need a dirt bike for gravel roads. I actually spent many years back in the 80s/90s running an XJ900 Yamaha on Aussie dirt tracks. Even managed to collect a roo at 100 kmh at one point. It had Fournales gas sealed rear shocks and a spotlight but no other mods. It handled the dirt well and was very stable, the shaft drive was a bonus when crossing flooded creeks but being a road bike there was a lot of stuff to shake loose from vibration. If you take a road trim C5 on dirt a lot keep an eye out for a few more things than normal vibrating loose, or falling off.