We're in Kazakhstan right now and just left Kyrgyzstan. Access to petrol is not a problem. There are numerous stations on all the major roads. When we went on the minor roads we made sure it was never more than 400km to next sizeable town.
Once and a while you may have to settle for 80 octane instead of 93, but it our mileage efficiency didn't suffer too badly. Fortunatly not a problem for bikes, but there is some really nasty diesel out there.
Petrol in both countries is just under a $1US per litre.