If you drive from Khartoum to Wadi Halfa you have to options:

1)
Follow the trainline:
I didn’t go there because IMHO this is not a good option for a single biker. As far as I know there is totally remote after Abu Hamed. Don’t know if you will find petrol, water or people.

2)
Follow the Nile:
The road is tarred to Abu Dom. They are working on a new “road” from Abu Dom to Dongola but in August there was mainly tracks. There are some sandy spots but it’s not deep and it is possible to avoid it if you plan carefully. You pass some villages on the way. When you get closer to Dongola you might see the new road. Dongola is a nice place to spend the night and have a meal or two.

I crossed the Nile in Dongola and then the sandy tracks goes through a lot of villages for a while. I have heard it’s possible to cross the Nile a bit more north to avoid that. When the villages is ended there is almost no more sand but the road is badly corrugated. The road reminds a bit on the road from Isiolo to Moyale (not the scenery), it’s not difficult but you get tired of the shaking. There are some villages on the way and it’s possible to get cold Nile-water, some places they even have Coke :-)) Didn’t see any bottled water.
The people in the villages are very friendly so I spend some time in different villages and used two full days from Dongola to Wadi Halfa.

The wind is normally from north to south and I had some sandstorms and got a bad mileage. Found petrol in Abu Dom, Dongola and Abri (black market).
You will meet people in the villages but I only met two cars on my two days from Dongola to Wadi Halfa.

I guess this is the easiest way to cross Sahara, but after all it is a dessert and the track doesn’t actually follow the Nile so bring a lot of water.
The last day I had a puncture. When I fixed it (more then 50 degrees and no shade) I drank almost all my water. I didn’t know by then because it’s hard to know how much water that is left in a camelback inside the jacket. When I left I tried to not drink more then a mouthfull for every kilometer and even if that sounds a lot I dried out. When I reached the first village I was in bad shape (lips, throat, week, dizzy)....
But right now it is a lot colder so if you take care it should be no problem!

Good luck,
AliBaba