Here is a complete guide for cycling from Samarkand to Bukhara, it is formatted for easy printing and can be downloaded from Scribd for your own use if you want it electronically. It has distances, camping, food and directions for the whole 275 km.
The route is quite straightforward and drops from 710m to 350m in the first 90km, then remains pretty flat for the rest of the ride. It never feels very difficult and while the road surface isn’t always great, it is generally pretty good. Every time it gets bad it seems as though it gets resurfaced.
We managed to ride from Samarkhand to Bukhara in 2 days, averaging about 22km/hr but we did have a gentle wind pushing us along. If the wind is in the wrong direction there is no escape.
Camping is easy once you realise that the Uzbeks are super friendly but will generally leave you alone. Drunk O’clock is about 2.30 as lots of people driving across the country have a bottle of vodka with their lunch. The roads are so wide and empty that this is no issue although groups of men in cars sometimes get a bit frisky.
The nicest time is around 1-2 hrs before sunset when all the families are sitting outside their houses along the road and this would also be a good time to ask if you could camp on a families land. We slept in fields with shepherds or just by the road in the trees with no problems.