Im leaving on a similar trip in about 2 weeks.

Iran, definitely a carnet needed and its a shame. Like Carl said, Iran is beautiful and amazing but the cost of a carnet is too high and what would happen if ones bike gets stolen? I guess no bike and no deposit

Its very difficult to get Russian visa, you need to get a travel agency involved and things like this. Maybe easier for you but for Poles its very hard. So im opting for a ferry through Caspian sea