[ChuffedToBits]

Not too difficult, really. Kyrgystan and Tajikistan especially are very popular with bicycle travelers, there's an established tourist infrastructure in the form of guest houses and homestays.

Border crossings into Uzbekistan and Turkmenistan are a nightmare (on some crossings they will demand your unlocked phone to rifle through and have you unpack ALL you luggage onto a blanket). Once you're in the countries it's usually just the odd corrupt official, but I was able to out-wait and charm my way out of those situations.

Biggest headache imho: Almost every Westerner I met had some kind of digestive problem. I suffered from diarrhea coming and going for about two months.

There's motorcycle rentals and guided tours out of Osh, Kyrgyzstan, that will also tour the Pamir Highway and Wakhan Valley in Tajikistan. Highly recommend you check out photos from the area around the Issyk Kil Lake on Google Maps. It's just stunning up there.