Spring again, and I’m having the motorcycle fantasy. What I’d really like is a Suzuki Bandit 400. I saw one while I was living in Taiwan, but it seems that in the US the only sport bike under 600cc is the Ninja 250. Any guesses?
Kawasaki has the Ninja 500cc model (500R), and Suzuki has the GS500F, the Buell Blast is 500cc, also, but the 400cc sportbike seems to be quite lacking.
Buy a dirtbike and put street tires on it. 
Because we like big bikes.
That’s not really the answer, but it is a clue. The real problem is that your question isn’t one I can answer. The question I can answer isn’t “why don’t we have them” but rather “why do other people”.
In several countries that are not the US (including Japan, although I’m not sure about Taiwan) the licensing system for motorcycles is graduated. There are typically three classes; under 250cc, under 400cc, and unlimited. Earning an unlimited license is difficult (if memory serves, it is on par with earning a class A racing license in the states). Thus, there is a huge market for Really Fast Motorcycles that displace 399ccs.
After doing a little research, I found that Taiwan calls theirs “Large sized Heavy, Heavy, and light”, and the break is at 600ccs. Here is a reasonably good article on the subject:
If your question is “what bikes are available”, rather than “why aren’t there 400cc sport bikes available in the States”, please feel free to disregard this post.
WAG alert.
Until the early '80s 400cc 4-stroke bikes were commonplace in the US. I think things started to change when a tariff was created for import bikes over 700cc. Previous 750cc bikes were changed to 699cc. That shifted the niche of 650cc bikes and possibly created a domino effect.
Thanks! The licensing thing sounds plausible. When I saw the Bandit in Taiwan it was back in the days when 150cc was the legal max (outside of a very exclusive group of special license holders, bikes that were grandfathered in when the restriction was passed, and folks who just flaunted the regulations), so it was most likely brought in from somewhere else in NE or SE Asia. I thought it was the perfect size for the kind of urban / suburban / occasionally longer rides around here. Is 400cc really too small for long highway rides? My little 135cc Yamaha RZX 2-stroke did three day rides and could go 160 kph (downhill with a tailwind). Appreciate the replies! Keep 'em coming!
I took my 1981 Honda CB400T (street bike, not sport bike) on some long rides. It didn’t much like hills, or going over about 65 or 70mph, but it was pretty old and decrepit at the time.
The important bit here is “2-stroke”. Two-strokes won’t pass EPA restrictions.
Okay, this is pure speculation. Motorcyclists (as opposed to “bikers”) tend to like speed and maneuverability. Racing machines. Or at least they want bikes with components and engineering that are “race tested”. The two main displacement classes in the U.S. appear to be 600cc and 750/1000cc. The 125cc two-strokers aren’t usable on U.S. roads because of their pollution. So people buy 600cc and larger bikes because that’s what the racers use. Manufacturers make 600cc and larger bikes because that’s what people are buying, and it’s also cheaper to have two engine sizes instead of three.
I really wanted a 1986 Yamaha FZ-400 I saw. Mint condition, almost no mileage.