I did this route solo in June last year, and was pretty apprehensive about the road conditions etc. The map I had showed it as unsurfaced, and the locals didn't agree on how difficult it might be.
As Colebatch said, on an adventure type bike you'd have no worries doing most of it at 60MPH. In the dry.
Without rain you'd manage it on a road bike, but it may take you all day. There is petrol en-route, but the station didn't look like the kind of place to adhere to any hard and fast opening hours.
Might be a wise idea to carry extra fuel unless your bike is good for long long fuel range.