I will certainly admit, an air-cooled bike likes to have some speed on its side. Motocross used to be a faster sport than today, but I imagine a high-rev-low-speed racing environment like Supercross would really put the strain on an air-cooled machine. For the kind of riding I like to do, however, which largely consists of desert and forest roads (yes, you can go from deep forest to barren desert in five minutes here in Oregon) there's always a lot of air flowing over the cylinder.
There are a lot of things I love about my Husky, but I've always been dissatisfied with its cooling. It fell victim to the widespread fin-shaving campaigns everyone was participating in during the early-80s, and it shows. I was drilling my friend on bike identification (because I could) and showed him a string of Huskies, asking for displacement. I showed him a lot of '70s models, then I showed him an '82 250. He thought it was a 125! Even Maico, who were always great with cooling, sold their soul a bit. While their cylinder looked the same, and the fins actually stayed fairly consistent, they constantly removed more and more of them. Take a look at an '83 and compare it to a '74 radial. Have a look at the distance between the lowest fin and the cases. On the '83, you could put a beer there. On the '74, you might fit slice of bread, if you mash it with your fingers.
No wonder everyone switched to water cooling. The air cooling didn't work, because they took 50% of the cooling surface away whilst cranking the power ever higher! That's not to say the big fins worked as well as radiators; they didn't, but they got the job done as well as needed, and gave the bikes yet another layer of personality that we have been duped out of lately. Well, I should say, the personality that
the rest of you have been duped out of.