I just returned from Africa. I bought a motorbike in Cape Town and drove up to Kenya (8 countries). I could manage perfectly without a carnet. Only Kenya seemed more difficult but if you can make them think for sure that you are not going to sell it there, no problem. Other people we met said it is the same in northern Africa (we planned to drive up to Spain in the first place, then changed our minds), and specially easy is ... Sudan. Maybe the big problem may be Egypt. My suggestion is to forget the carnet, too expensive and takes a couple of weeks. Also, to get the money back -of the deposit- may take a while. Not worth it, better to try.