This is an endless debate. People will never agree on what makes a good touring bike just as they will never agree on what makes a good Pizza. Depending on experience and personal preference, everyone has different ideas. For some, anything less than a full dress luxo-barge like a Goldwing or an Electra Glide is unthinkable. For others, a 250 cc scooter is just fine. There actually is a group of scooter touring enthusiasts (Scoot-Tours) and they mostly ride the 250cc Honda Helix -- go figure!
I think the important attributes of a touring bike are, in order of priority,
The cost of the bike goes in there somewhere but I'm not sure where. You will most likely have the same categories but not necessarily in the same order.
The appropriateness of a particular machine depends on your unique style and priorities.
Americans are obsessed with large displacement motorcycles and I can't tell you how many times I've heard someone say that you can't tour on a bike with less than 750 cc (or 900 or 1000, or 1200 or whatever). I think that this is an extension of the generally silly "Bigger is Better" mentality that seems to dominate the American thinking on most subjects. This thinking is absolute rubbish. Bigger bikes usually have more powerful engines and more power is nice to have but it's not the most important characteristic of a motorcycle. Notice that power isn't even on my list. As long as it meets the criteria I've listed above, any motorcycle can be used for touring.
I'll repeat that; Any motorcycle can be used for touring.
I have to admit that I have a preference for smaller displacement motorcycles. All other things being equal, smaller displacement bikes have better handling and just feel more nimble. I have owned several 1000cc bikes but find their weight gets in the way of the fun factor. That doesn't mean that I have no use for large bikes. Even today one of my bikes, a '78 BMW R100/7, is a large displacement bike. However, an old BMW airhead is hardly a cutting edge performance bike. It's still fun to ride and is relatively light for a 1000cc bike.
I think that one reason many people prefer larger displacement bikes is that many riders equate the ability to go fast in a straight line with rider skill. The reality is that there is no relationship between fast straight line speed and rider skill. Bigger bikes have higher top speeds because they have more horespower, pure and simple. Straight line speed is a function of horsepower and the willingness to use it: it has nothing to do with skill. Many riders are simply deluding themselves when they think that because they can go fast in a straight line that they are good riders. The skill in operating a motorcycle comes into play in the turns.
This seems self-evident but you wouldn't believe the number of bikes I've seen along the side of the road in the middle of nowhere with something basic broken like a drive chain which should have been replaced 5000 mi. (8000 km) ago.You don't want to spend several days of your trip broken down in some small town waiting for some obscure part to be delivered. My point here is that if you tour on a bike that needs maintenance or is prone to failure like an old Norton or 70's vintage Triumph don't be surprised when it breaks. According to MTS, the most common on the road failure in motorcycles is dead batteries. This particular problem is usually entirely preventable by replacing the battery before it fails. There are other pages with more information on topics related to maintenance and preparing the bike for a trip.
You can either buy a bike in good condition and then properly maintain it or buy a junker and fix it up. The later is sometimes cheaper but is a lot of work and you need to know what you're doing. Older bikes (middle eighties vintage and earlier) tend to be less reliable than newer ones but a ten-year-old bike that's been maintained properly will still run for 60k to 100k mi. (96k km to 160k km) without any major problems.
It won't do you any good to have a reliable bike if you feel like you've been tortured by the Marquis de Sade every time you go for a ride. That being said, there are no hard and fast rules as to what constitutes a comfortable bike. Goldwings and the like are generally considered to be the most comfortable bikes around. While they are certainly pretty good I don't like them because their sculpted seats force you to sit in one place. You can't move around on the seat, which is something I like to do. There is one universal principle though -- you need some way to deal with the windblast.
Standard motorcycles (a.k.a. "UJM" for Universal Japanese Motorcycle or "naked bikes") have a "sit up and beg" riding position and usually have zero wind protection. As manufactured they can be exhausting to ride for any significant distance at any reasonable speed. You need to hold on to the bars for dear life while constantly flexing your stomach and lower back muscles to fight the wind. An after-market windshield usually solves this problem nicely. Since standard bikes are not as common as they used to be, there are not as many companies manufacturing after-market windshields. A couple that I am familiar with is National Cycle and Rifle. They both have a large variety of windshields available. If you know of any other vendors please let me know.
The only caveat on a windshield is that it be the proper height and shape. Some windshields can create turbulent airflow near your helmet which can jerk your head about like a rattle in the hands of a small child. It can be worse than the windblast you were trying to eliminate. Usually, the solution is to use a shorter windshield. It won't stop all the windblast but it will stop enough of it and the airflow will be smooth. I prefer shorter windshields. I like to look over the windscreen, not through it. I also like to have some airflow around my helmet. It's cooler when it's really hot out and it clears the rain off your helmet's face shield. Looking through a windshield in the rain can be dangerous. Most motorcycle windshields do not clear the rain very well and will severely distort your forward view if you have to look through them in the rain .
Don't let the size of the windshield fool you. Even small windshields can provide acceptable protection. The windshield on my KLR650 is so small that I thought it was a joke when I first saw it. It works amazingly well and I can do 500 mi. (800 km) days on it with no problems. I've seen some after market bikini fairings that offer great protection and large frame mounted fairings that are completely useless. The bottom line here is that you can't always predict the effectiveness of a particular windshield on a particular bike until you try it out.
Another thing you can do to improve your ability to resist the windblast is to adjust where the handlebar handgrips are located. Standards, crusiers, and dual sport's usually have tubular handlebars that can either be adjusted or replaced with a different curve to make you lean forward a bit. Even a small amount of forward lean can help a lot with windblast, even without a windshield. Changing the handgrip position on a sport bike can be more difficult. the degree of adjustment is dependent on the desing of the clipon's on the particular bike. On some sportbikes the handgrips are too low and actually need to be raise. There are at least two manufacturers that make bar risers, Heli Modified and Gen Mar.
Cruiser style bikes are pretty popular these days but they also have the same wind problem as the standard bikes. The solution is generally the same -- get a windshield. Cruisers have an additional problem with the seating position: at least I think that it's a problem. Your feet are farther froward, in some cases, a lot farther, than on other styles of motorcycles. The feet forward pegs when combined with the position of the handlebars tends to make your torso lean to the rear. As a result you must use abdominal muscles and your grip on the handlebars to resist the windblast. This can be quite fatiguing and also makes the bike harder to control.
For optimal control you should not be applying any force to the handlebars except the small pressures needed to initiate or maintain countersteering for cornering and general control. Applying forces to the handlebars for any reason not related to control is called bar loading and is a bad idea. It does not matter if you're loading the bars because of nervous tension, resisting windblast, or doing your daily exercise. It's a bad and interferes with your ability to precisely control the bike. Ideally your hands should be simply resting on the handle bar grips. You can also install a sissy bar and attach some of your luggage to it to act as a backrest. Even with a backrest, you still have to use your neck muscles to move your head down or else you'll be looking at the sky. There is a fair amount of variation among cruisers in the degree of "lay back" and therefore in the comfort level you can get.
Sport bikes are generally not considered touring bikes but a lot of people use them for touring, including me. My primary touring bike is a '99 VFR800 (and a '90 CBR600 before that). The relatively extreme forward lean, at least when compared with standards and cruisers, almost perfectly compensates for the windblast, at least above 45 mph (72 kph) or so. At lower speeds it's not so nice as all your weight is on your wrists and shoulders. There is quite a bit of variation in the amount of forward lean and wind protection in various sport bikes. If the clip-on is above the triple-clamp the lean is usually not too bad. If they are below the triple-clamp it may be uncomfortable. Your degree of comfort on a sport bike will depend on the length of your arms and torso, the size of the tank, the vertical position of the seat relative to the clip-on, how the fairing shapes the airflow, your phisical condition, and the size for your gut. For example, for me, a CBR600 is much more comfortable than a GSXR600.
Standard and Dual Sport Bikes both have the "sit up and beg" position and are quite comfortable as long as you've solved the windblast problem and have a decent seat. On both types of bikes your feet are more or less under your thighs and you can stand up on the pegs if you want. It's nice to be able to stand on the pegs as you can use your leg muscles to absorb bumps and reposition your butt on the seat.
Cruisers force you to put your feet out in front so far that you can't use your legs as shock absorbers and all your weight is on your tailbone. The shock of every bump goes straight into your spine. Also, on the classical cruiser you grip the bars near shoulder level - too high for good spinal position. This all can get real uncomfortable and is the main reason I don't like cruisers.
Sport bikes position your feet further back and higher than a UJM. There is a lot of variation from bike to bike in foot peg position and even an inch can make a big difference. On my CBR600 the pegs are about an inch lower and an inch further forward than on a GSXR600 and it makes all the difference in the world. You don't so much sit on a sport bike as you squat on it. You'll notice this after your first long day; your thighs will feel like you've been doing squats in the weight room. After you're conditioned to this it's not a problem but it is different than other typesbikes.
You'd be surprised what shape of person can fit on a sport bike. I'm not a small person; I'm 6'3" tall (191 cm) and weigh 185 lb. (84 kg). I'm also 51 years old and those old joints aren't as limber as they used to be. Even with all that I can ride my CBR600 all day, day after day. It's not that I'm tough or like pain because I'm not and don't. The bike is just that comfortable. I'm also in fairly good physical condition. Touring on a sport bike is really nice when you get to some serious twisties. Sure, twisties are probably fun on any bike but they're more fun on a sport bike.
There are three things to consider about the seat: its firmness, surface texture, and shape. I prefer a firm almost hard seat. The plush pillow-like seat on most cruisers may seem like it would be a good seat for the long haul but I've found that the foam is too soft and after several hours you are essentially sitting on the seat pan and it can get pretty hard. Also, after a long day those nice tuck and roll seams form little ridges that can really dig into your butt and thighs, especially when it's hot out. Standard, Dual Sport, and Sport bikes tend to have relatively flat and firm seats. Some are firmer than others but at least there are no seams to dig into your butt.
The shape of the seat can be important. I like a flat and fairly wide seat so I can move around. I had a Corbin on my old Concours and as far as firmness goes it was wonderful. The problem was that it was dished so much that there was only one place that you could sit and while it wasn't a bad position you were constrained to sit in that one place all the time. On tour, it's nice to be able to move around, it helps minimize butt burn. Dual sport bikes tend to have relatively narrow seats with pretty soft foam and can be pretty uncomfortable for more than a couple hundred miles. I had the weat fo my KLR650 reshapped to make it a bit wider and had the foam replaces with the stiffest foam I could get. It's now much more comfortable for longer rides.
A note for those vertically challenged riders out there, particularly those under 5'5" (165 cm).This probably includes most women. All motorcycle seats are somewhat triangular in shape with the narrow end near the tank and your butt normally sitting the wide part. They have this shape so that the edge of the seat doesn't dig into your thighs. This will only work if your calf is long enough. Shorter people tend to have shorter legs and when seated on a motorcycle their thighs are lower than normal. Sometimes the seat digs into their thighs. This can be very uncomfortable. If this is happening to you, you may find that additional narrowing the forward part of the seat can help. It will also help you reach the ground better, effectively lowering the seat, because when you put your feet on the ground your thighs are not forced as far to the side as much so your legs can go straight down from the hip. The Short Bikers Web Site is a great resource and has a lot more information on altering a bike for shorter riders.
The last seat quality is texture. You want the seat to have a little grip. Do not put Armor-All on your seat unless it has significant texture features in the plastic. Armor-All will make the seat very slippery making the bike hard to control as you're sliding around. You don't want too much grip though. You wany to be able to move around on the seat with a minimum of effort.
The bike's ride quality can make all the difference in a comfortable trip. The two primary considerations are suspension harshness and engine vibration. The relatively stiff suspension on sport bikes helps them handle well but long days on less than perfect roads can really pound you. This is not fun. You can buy a more capable after market shock but this will be pretty expensive. The really soft plush suspension, like those found on most cruisers, is very comfortable on reasonable roads but on rough roads the suspension can bottom out and they can feel like you're about to compress your spine.
In general, you want a properly setup suspension that is compliant. That means proper sag (spring pre-load and spring rate) and proper compression and rebound damping both front and rear. Most bikes (including many sport bikes) come from the factory with marginal to crap suspension components. Compound that with the fact that most riders don't have a clue how to properly setup a suspension (if the adjustments are even there) you have a recipe for lousy ride quality AND lousy handling on many of the bikes on the road today. For more information see the Maintenance section.
Another comfort consideration is engine vibration. What seems like a minor vibration for a few hours can be exhausting after 500 mi. (800 km). How much is too much varies a lot from person to person. You'll have to decide how much and what kind you can take.
Motorcycle riding is about having fun. For me the essence of riding is leaning into the turns and the more lean the better. That's why I like sport bikes so much -- they can achieve substantial lean angles without scraping hard parts. This characteristic also makes sport bikes a bit safer. You have more margin in corners. If you come into a corner a bit to fast you almost always can lean a little further and make it through the turn without scraping anything. Sport bikes also have more precise steering and just generally handle better than other types of motorcycles.
Lean, or the lack of it, is why I dislike crusiers. They have such low ground clearance that you will be scraping hard parts well before you even approach decent lean angles. Cruisers also have relatively slow steering and their handling is best described as ponderous. I admit that crusiers are not designed for spirited riding and it's not really fair to criticize them for poor handling and lack of ground clearance. Still, I'll do it anyway -- it's my web site. If you're into "Smell The Roses" riding, a crusier may be good choice. They just aren't my cup of tea.
Dual sport bikes have essentially limitless ground clearance and lean angles are limited only by tire traction. They do tend to have rather flexible frames and poor suspensions so they don't generally handle as crisply as a sport bike. Still, they can be a blast to ride and with higher quality after-market suspension components and ultra-smooth riding technique a dual sport is nearly the equal of a sport bike in the twisties.
In general, the less stuff you take with you the more choices you have as to the sort of bike you can use. The two carrying capacity considerations are weight and volume. Generally, the bigger the bike, the more volume it can carry. The ultimate bikes for cargo volume are the big rigs like the Goldwing, Electra Glides, and BMW R1100RT. These bikes all come with hard saddlebags and tail trunks and have room for mind-boggling amounts of stuff. If you're one of the kitchen sink crowd and need even more room some can also tow a trailer.
Make sure that the GVWR of the bike is consistent with what you want to carry. The GVWR is the maximum weight of the bike, fluids (oil, gas, and coolant), rider(s), and gear. You have to be careful here. When you do the math you will find that many bikes have quite a bit less cargo weight capacity than you would think. See the section on Packing The Bike for more Information. If you ride solo (one person per bike) you will have a LOT more capacity.
Even if you're riding solo, you still have to attach your gear to the bike. If you have a luxo-barge there are probably enough nooks and crannies to pack things. However, standards, sport bikes, and cruisers vary tremendously in their ability to simply attach stuff. Look for bungee hooks or frame rails on the rear of the bike. Often there's nothing there but pretty body plastic and attaching gear is damn near impossible without major modifications. On other bikes there are real nice bungee hooks or other means to attach tie-downs.
A few bikes have the fuel filler under the seat - this can really be a pain on tour. If I remenber correctly the old Yamaha 550 Virago is one of these bikes. You don't want to have to take everything off the bike every time you want to fill the gas tank.
By range I mean both comfort range and fuel range. I've already covered comfort so I'll not dwell on it. Fuel range is tank size times mileage. Most bikes get around 40 to 50 mpg--some less, a very few get more. With a given bike the mileage can vary up or down depending on speed and how smooth you are with the throttle, just like a car.
I think that you should have at least a 150 mi. (240 km) range without going on reserve. For most bikes this means at least a four gallon tank (assuming 0.5 to 0.9 gal reserve). This is not so you can be a "Real Man™" and ride a jillion miles nonstop. The reason you want the 150 mi. (240 km) range is margin and flexibility. If you get out in the mountain west of the US or Canada there are many places where it's at least 125 mi. (200 km) between gas stations. Just about anywhere in the US it can get hard to find late at night gas if you're not on an Interstate. The more gas your tank can hold the better off you are. Running out of gas sucks. Running out of gas 50 miles from the nearest gas station sucks a lot.
There is a trend, particularly among cruisers, to mount teeny tiny gas tanks with capacities in the two to three gallon range, including reserve. This is a purely cosmetic thing and totally stupid as far as I'm concerned. One saving grace of the small tanks is that most of the bikes with the tiny tanks are so uncomfortable that you'll be forced to stop after 80 mi. (130 km) because you'll be sore, exhausted, or both.
Small gas tanks are not limited to cruisers. The Honda VTR 1000 has a particularily small tank for a sport bike. I don't recall the exact fuel capacity but a range of the VTR is something on the order of 120 miles or less. This is an absurdly short range for a motorcycle that is generally considered to be a sport touring bike. If I were being generous I'd say that Honda had a lapse in judgement when they mounted such an inappropriately small tank on what is an otherwise fine motorcycle but it's outrageous that Honda continues to mount the same size tank on this bike three years after its introduction. They should know better.
The point here is that you shouldn't assume that a bike you're thinking of buying has an adequate fuel range. Check out the fuel capacity and the mileage and be sure that ratings will meet your needs.