Originally Posted by JADM
I like fours over twins.
is there any reason for your preference?
how do the engines compare in longevity
Yes. Fours are smooth and powerful. (I hate blanket statements, but there you go.) I wore out a Honda Magna with a V-Four. It lasted 21 years. The Honda CB400F Super Sport (inline four) that I had before that lasted 11 years, and it was running fine when I sold it. I suppose that the racing style Japanese inline fours might wear out sooner, especially if ridden hard at track days and such, but I have no experience with them.
I truly want to like the common V-Twins (e.g., Harley-Davidson), especially the cruisers. I like the relaxed riding position. Sadly, every time I ride one I am reminded of the vibration, even the ones with rubber mounts and counter balancers, and they have relatively low power. I have ridden the "new" V-Rods, too. They are better, but I still have the same overall complaint.
I have borrowed an R1200R (boxer engine, opposed twin) several times, and sometimes have had it for over a week of daily riding. It has plenty of torque, which was very cool, but the vibration characteristics still weren't to my liking. I have also ridden the BMW F800ST, and several Ducati's. The Ducati's were smoother than most twins, by the way.
I just tried a Victory Vision last Saturday. It is such an interesting looking bike, and I thought that it might encourage my wife to ride pillion with me again. What a slug. I can't imagine what it would be like with the cases full and a pillion on back. Same vibration issues, even in the highest gear at freeway speeds. My hands started to go numb after only a few minutes.
In addition to the vibration, twins usually have a much lower maximum RPM compared with fours. Depending on the bike, this translates into more frequent shifting, especially in city traffic. It also means that you have to be more precise in choosing the right gear for a given speed. Many fours have broad power bands that allow you much more flexibility with respect to how you choose to shift.
Each time I try a different bike, it just gives me a greater appreciation for my K1200GT, warts and all. I can't really describe that warm and fuzzy feeling of climbing on the GT and riding away after trying something else that just doesn't suit me as well.
To repeat myself, I really want to like twin engine motorcycles, but it just never seems to work out. Obviously, lots of people disagree, and prefer the twins over the fours, and I am pleased that they have found what is right for them.