The bottom line is that simple is best. Generally speaking you will need to fix anything that goes wrong on your bike and therefore the fewer things that can go wrong the better. The engine should be easily accessible and easy to work on and to this end the ideal would be a single cylinder air-cooled engine with little in the way of fancy electronic gadgets. Water-cooled engines are completely unnecessary, they provide no real advantage over a well-tuned air-cooled engine and are just another thing to break (usually the radiator) or go wrong. An oil cooler can be added if you are going to be travelling through very hot countries though generally it is not really necessary. A kick-starter (to get you out of trouble if you are going off-road) along with electronic starter is advisable also.

Weight
If you are not planning on going off-road then weight is not so much of and issue other than normally the heavier the bike the worse the fuel consumption. If you do plan on going off-road, then weight is very important and the lighter the bike the better. When loaded up with all your kit (60kg+) most bikes will soon loose any off-road agility they started with and fuel economy will plummet as well.

Fuel economy
It is important to go for a bike with reasonable fuel economy and an average should be about 50mpg/17.5kpl. Most two-strokes engines cannot reach this figure so stick to four-stroke engines. Always bear in mind that when heavily loaded and off-road, in soft sand or mud, fuel economy can drop drastically, sometimes by as much as 25%.

 

Main tank size
It is a good idea to choose a bike that has a reasonable large main tank; this avoids the problem of carrying too many spare fuel containers. If you are going to stick to the black stuff then it is not as essential but still makes life easier as you do not have to continually worry about where the next fuel station is. If you are going off-road, and in particular if crossing long tracts of wilderness like deserts, then having a large main tank is essential. Carrying too many heavy fuel cans too far back and/or too high up on your bike will not only stress your bike unnecessarily but will reduce its off-road agility. As a guide, look for a tank capacity of between 20 and 30 litres or more, or add a bigger after market tank (Acerbis do a great range of large plastic tanks).

Durability
You will undoubtedly drop, fall-off or crash your bike at some stage during your travels and to this end it is very important that your bike is durable enough to cope with these little accidents. Sturdy parts like wheels, forks, control levers etc and no unnecessary plastics, which are easily broken, are a must, one off-road tumble can literally write-off some unsuitable bikes.

 

Off-road suitability
If you are expecting to spend a lot of time off-road then you will need a bike that is up for the job. Light overall weight, low seat height, high ground clearance (including a bash plate), tight turning circle, 21" front wheel, knobbly tyres etc would all be ideal for off-road riding, and pretty much describes your typical modern trail bike. However, be aware that what is ideal for off-road is generally not so good for basting down tarmac roads for long periods of time.

Road bikes
If you are travelling across North America or heading out to India it is quite possible to stay on road all the way, and if you have no hankering to blast of into the wilderness then a road bike is ideal. Big old touring bikes like BMW's R series, Honda's Gold Wing and Triumph's Trophy are all fine. Alternatively you could take the stance that your bike is expendable and therefore choose any cheap and simple old four-stroke like Suzuki's GS series, Kawasaki's GT series and Honda's older CB series, and if it dies en route bury it and move on. This may seem a little extreme, but so long as the bike is mechanically sound and well prepared there is no reason why it should be less suitable than any other bike, and it is probably much less likely to get nicked.

 

Dual-purpose bikes
It is pretty much guaranteed that at some stage on your travels you will spy that track which leads off into the distance, or see that wide open space stretching away and be sorely tempted to go for it! It therefore makes sense to anticipate this and choose a bike that can handle these conditions. The dual-purpose bike, which is a cross between a road and a trail bike, is perfectly suited to the varying road conditions encountered whilst travelling overland. Large tank, light weight, comfortable saddle, supple suspension, high ground clearance, good off road steering geometry and simple, balanced engines are a hallmark of this class of bike, though some are better than others. Yamaha's XT(Z) Ténéré and Super Ténéré series are great all-rounders, though the earlier 600 cc versions are the pick of the bunch. Honda's XL 600 series (the LM is best as it has a big tank) is good and the big V-twins XLV600VP Transalp and XRV 750 Africa Twin are worth a look but perhaps a little to heavy for serious off-road use. BMW flat-twin engine GS series is much loved by overlanders the world over, though somewhat heavy, their low centre of gravity makes them ok off-road if not brilliant. The F650 Funduro, with its Aprillia built Rotax engine (a little too revvy for serious off-road use), makes a fine touring bike. Other possible bikes include Cagiva's 750/900 Elefant, a fast, road oriented touring bike and KTM's 640 Adventure, perhaps a little too good for the average overlander.