As others have said, forget about cycling with a backpack. (Ultra)light camping luggage would realistically be in the range 10-15 kg. 15 kg gets you a comfortable outfit. If you spend more you can reduce the weight to something like 13 kg. 10 kg is possible, but assumes that you buy expensive ultralight stuff, and also that you give up quite a bit of comfort. 10 kg would fit in a 24 litre Carradice Camper Longflap saddlebag plus a large handlebar bag like a 12 litre Gillles Berthoud. Such a heavily loaded saddle bag needs a sturdy support like the Nitto R10 rack (or a regular pannier rack). If you want to do a trip like this on something like a road bike, this is the way to go.
If you have a touring bike you can take a bit more, and if you do, rear panniers and a handle bar bag are the way to go. Pacific Outdoor/Hyalite ltw small panniers
http://hyaliteequipment.com/bike-gear/view/ltw-small-pannier-bike are light (just over 1 kg the set) and with 36 litres big enough. Ortlieb bags are probably sturdier, a bit larger, at 40 litres, but also considerably heavier (1900 grams, but the cheaper City Line about 1500 gram). Put the wet and dirty tent on top of the rack (no need to have it inside a bag).
The trick is to keep volume down. The best area to do so is with the sleeping kit. A down bag packs to the smallest size, and if you have the money, PHD are the brand to look into (esp their special sales offers). Polish brand Cumulus or British Alpkit are more affordable offerings. Mattresses are another area where you can reduce pack size significantly. Self inflating mattresses as a type have been overtaken by modern insulated air mattresses. The Thermarest Neoair Allseason is the leading model for north western European conditions. The Exped synmat basic is a slightly heavier and more voluminous budget alternative. For really cold weather the Exped Downmat is the one to get.
Stoves. This is as much about fuel availability as anything else. So in the third world (or in arctic conditions where nothing else works) a multifuel stove is the thing to get. But they are expensive, heavy, and fiddly. Canister gas stoves are convenient, cheap and light, but the (expensive) gas is sometimes hard to get. The bad news is also that there are two standards for valved canisters: the Lindall Valve screw type and the Camping Gaz type bayonet connection. In France, the latter is almost the only kind you can get, but elsewhere it is the other way around. Primus do a special (sometimes hard to get) Duo version of their Express canister top stove that will take both kinds. There are also various adapters but these obviously add bulk and weight. My personal preference is for a meth stove, and the Trangia 27 UL HA in particular.. This is marginally heavier, but very convenient in use, particularly in windy weather because no other stove has as good a windscreen. The Clikstand and the Caldera Cone are ultralight meth stoves, but more suitable for heating up ready made meals than for cooking real food.
Tents. Ultralight solo tents like the Terra Nova Laser Competition or the Vaude Power Lizard are around the 1 kg mark, and are what you should choose if you opt for the 10 kg target. The Wildcountry Zephyros 2 Lite 2013 will be a cheaper and almost as light alternative. For really bad weather the superb but expensive Hilleberg Akto is the one to take. MSR also make a few nice and light tents, but avoid the US style models with an all mesh inner tent (they are for hot and muggy weather). If you don't mind a bit more weight, the 1.7 kg Hilleberg Anjan 2 is superbly made, palatial, and expensive.
So make up your mind if you want to use a saddle bag or panniers. If you go for a saddlebag, tick all the ultralight boxes when you are choosing gear. If you are taking a road bike, this would be the best way to proceed. If you care for a bit more comfort, you need a somewhat sturdier bike that can take wider tyres and is a bit more stable. If you want comfort, this is the way to proceed. Comfortwise, there is vast difference between a 10 kg outfit and a 13-15 kg outfit. Financially, a 15 kg outfit is possible without breaking the bank too much.
Enjoy,
Willem
